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91.
零炮检距数据在海洋地震资料处理中有很多优势和用途,然而,受海洋水平拖缆地震采集作业方式的限制,接收数据的最小炮检距一般在200 m左右,小于该炮检距的数据是无法直接获得的.通常的做法是通过对较大炮检距数据进行动校,通过外推来变相获得零炮检距(包括小炮检距)数据,其外推的精度会受到地震资料信噪比、动校正速度的精度等因素影响,并且保幅性较差.本文通过一种基于Kirchhoff真振幅偏移和反偏移串联的技术,在反偏移过程中改变观测系统,有效实现了大炮检距反射地震数据向零炮检距(包括小炮检距)数据之间的转换,且很好地保持了零炮检距(包括小炮检距)数据的振幅特性.同时,经偏移-反偏移串联处理后,有效压制了地震数据中的随机噪声,地震资料信噪比和成像精度均得到显著提高. 相似文献
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在全球气候变化和人类活动影响加剧的背景下,作为河口海岸重要子系统的三角洲正在发生快速变化。长江三角洲地处长江入东海交汇处,是中国最重要的经济核心区之一,对邻近区域乃至整个长江经济带经济社会发展都起着重要作用。由于全球变暖、海面上升和强烈人类活动引发了三角洲系统状态转换,因此以往基于恒定系统状态而获得的有关长江三角洲的认识已不能满足未来需求,迫切需要对未来海面变化、极端事件、流域与河口工程影响下的三角洲物质循环条件、物理过程、地貌冲淤演化、源-汇格局调整等科学问题进行深入研究。在三角洲系统行为、未来演化趋势的预测能力建设中,应重视从海面到海底的综合立体观测系统的发展,以获取关键数据;基于三角洲系统的时、空演化特征,建立三角洲本征态和衍生态的谱系理论。未来需针对系统状态转换而调整原先的经济社会发展模式,以便保护自然资源、重建生态系统,更好地支撑长江经济带发展,重绘长江三角洲发展蓝图。 相似文献
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海域分等定级是制定海域使用金征收标准和开展海域资产价格评估的前提和依据。借鉴《海域定级技术指引(试行)》,遵循资源禀赋差异、收益差异、节约利用和生态用海的原则选取海域自然条件和海域区位条件2个定级因素及海水质量、海洋自然灾害等10个评价因子,构建深圳市浴场用海定级的评价指标体系。采用综合指数评价法计算出207个评价单元的得分情况,通过聚类分析方法和变异系数(CV)来校核级别,最终将浴场用海的海域划分为Ⅰ级(22.22%)、Ⅱ级(33.82%)和Ⅲ级(43.96%)3个级别。研究成果为海洋管理部门制定浴场用海不同级别的基准价格提供了依据。 相似文献
96.
褐菖鲉仔、稚鱼消化系统发育的组织学观察 总被引:1,自引:0,他引:1
为探究卵胎生鱼类褐菖鲉(Sebastiscus marmoratus)的仔、稚鱼消化系统组织学特点, 采用常规组织切片技术, 并用HE染色和组织化学染色, 比较分析了产出后0~50d的褐菖鲉仔、稚鱼消化系统发育的组织学变化。结果显示: 褐菖鲉初产仔鱼已分化出口咽腔, 并具有初始的食道、胃、肠、肝脏和胰脏; 2日仔鱼肛门与外界相通, 食道扩大, 开始摄食, 进入混合性营养期; 3~4日仔鱼幽门盲囊出现, 食道内壁出现黏膜皱褶5~6个, 胃黏膜皱褶5个, 肝细胞团区域扩大; 5~6日仔鱼卵黄囊和油球耗尽, 进入外源性营养期, 食道黏膜上皮出现杯状细胞, 肠道弯曲, 可区分前中肠和后肠两部分; 10~14日仔鱼食道环肌层明显, 黏膜皱褶增加到7~12个, 胃壁四层结构基本形成, 肠道黏膜皱褶加深, 纹状缘清晰可见, 肝细胞分裂迅速, 数量显著增加, 体积增大, 出现肝血窦和胰岛; 28~30日稚鱼出现胃腺和胃小凹, 已具功能性胃, 标志着稚鱼期的开始, 此时胰岛细胞数量和酶原颗粒增多, 消化能力显著提高; 47~50日稚鱼已基本具有成鱼胃的特征, 肠道纹状缘发达, 肝细胞呈多边形, 细胞内含大量脂肪颗粒, 消化系统从结构和功能上已趋于完善。由此可见, 褐菖鲉仔鱼和稚鱼消化系统的发育具有卵胎生鱼类发育较早的特点, 与其消化功能的完善密切相关。 相似文献
97.
The longitudinal functional connectivity of a river–lake–marsh system (RLMS) refers to the actual water-mediated transport of material from upstream to downstream areas along a spatial gradient and is fundamental to understand hydrological and biogeochemical cycles. However, due to a lack of consensus on appropriate data and methods, the quantification of connectivity is still a challenge, especially at the catchment scale. We developed a new method to evaluate longitudinal functional connectivity based on fluxes of materials (water, sediment, and chemicals) along a RLMS. The calculation of fluxes is based on the longitudinal pattern of terrain gradient, which influences transport efficiency, and on contributions from hillslopes, which set the initial spatial template of material loading to the RLMS. We evaluate the contributions from hillslopes to RLMS based on a new modified version of the index of sediment connectivity (IC) proposed by Borselli et al. (2008) and revised by Chartin et al. (2017).We applied this method to the Baiyangdian Basin covering an area of 3.4 × 104 km2 in China and quantified longitudinal functional connectivity during normal, wet, and dry periods(April, July and December) in year 2016. We found that areas with good structural connectivity exhibited poor functional connectivity during the normal and dry periods. Modelling testing with discharge data from hydrological stations and measured chemicals from Baiyangdian Lake was satisfactory in test periods. We conclude that public data and Digital Elevation Model-derived information can be used to reliably map the longitudinal functional connectivity of RLMSs. The proposed method provides a useful tool for monitoring and restoring the longitudinal functional connectivity of RLMSs and our results indicate that efforts aimed at restoring functional connectivity in RLMSs should take into account landscape patterns that can greatly influence fluxes in the watershed. 相似文献
98.
设计与开发的城市综合管线管理信息系统采用C#为开发语言,Visual Studio为开发工具,是以ArcEngine组件为基础开发的地下管线管理信息系统。本系统设计主要的研究内容为:对地下管线管理系统进行需求分析,地下管线系统的总体设计,包括系统的数据库设计和功能设计,编程实现了管线系统的用户管理子功能以及管线浏览、管线查询、管线编辑、管线分析的爆管分析等功能。基本满足城市地下综合管线统一管理的要求,对于提高城市地下管线信息的利用以及保障管线正常稳定运行都具有重要意义。 相似文献
99.
Forest structural diversity metrics describing diversity in tree size and crown shape within forest stands can be used as indicators of biodiversity. These diversity metrics can be generated using airborne laser scanning (LiDAR) data to provide a rapid and cost effective alternative to ground-based inspection. Measures of tree height derived from LiDAR can be significantly affected by the canopy conditions at the time of data collection, in particular whether the canopy is under leaf-on or leaf-off conditions, but there have been no studies of the effects on structural diversity metrics. The aim of this research is to assess whether leaf-on/leaf-off changes in canopy conditions during LiDAR data collection affect the accuracy of calculated forest structural diversity metrics. We undertook a quantitative analysis of LiDAR ground detection and return height, and return height diversity from two airborne laser scanning surveys collected under leaf-on and leaf-off conditions to assess initial dataset differences. LiDAR data were then regressed against field-derived tree size diversity measurements using diversity metrics from each LiDAR dataset in isolation and, where appropriate, a mixture of the two. Models utilising leaf-off LiDAR diversity variables described DBH diversity, crown length diversity and crown width diversity more successfully than leaf-on (leaf-on models resulted in R² values of 0.66, 0.38 and 0.16, respectively, and leaf-off models 0.67, 0.37 and 0.23, respectively). When LiDAR datasets were combined into one model to describe tree height diversity and DBH diversity the models described 75% and 69% of the variance (R² of 0.75 for tree height diversity and 0.69 for DBH diversity). The results suggest that tree height diversity models derived from airborne LiDAR, collected (and where appropriate combined) under any seasonal conditions, can be used to differentiate between simple single and diverse multiple storey forest structure with confidence. 相似文献
100.
Seyedsina Yousefianmoghadam Mingming Song Mohammad Ebrahim Mohammadi Brittany Packard Andreas Stavridis Babak Moaveni Richard L. Wood 《地震工程与结构动力学》2020,49(9):924-945
This paper discusses the dynamic tests of a two-story infilled reinforced concrete (RC) frame building using an eccentric-mass shaker. The building, located in El Centro, CA, was substantially damaged prior to the tests due to the seismic activity in the area. During the testing sequence, five infill walls were removed to introduce additional damage states and to investigate the changes in the dynamic properties and the nonlinear response of the building to the induced excitations. The accelerations and displacements of the structure under the forced and ambient vibrations were recorded through an array of sensors, while lidar scans were obtained to document the damage. The test data provide insight into the nonlinear response of an actual building and the change of its resonant frequencies and operational shapes due to varying damage levels and changes of the excitation amplitude, frequency, and orientation. 相似文献