Bed changes at toe of inclined seawalls

This study was carried out to investigate the scour phenomenon at the toe of seawalls and the different parameters that affected it. Experiments were achieved using different wave steepnesses, bed material grain sizes, wall positions and inclinations. Based on experimental results, the parametric plots of toe scour for smooth impermeable inclined seawalls were prepared. Also, this paper presents the bed changes prediction at seawalls toe using artificial neural networks on the basis of experimental data to widen the range of application. Suitability of using a neural network model was developed, and a model was validated. It is proposed that this model can be used in coastal engineering applications.     

溶剂萃取法分离锂同位素研究进展

锂同位素(6Li和7Li)在原子能工业中占据着重要的地位。在众多锂同位素的分离方法和体系中,溶剂萃取法是一种具有较高分离系数,并最有望实现无毒、高效分离的工业生产方法。阐述了溶剂萃取法分离锂同位素的原理,综述了醇类与酮类、烷基膦与膦酸脂类、冠醚类及其它溶剂萃取体系在锂同位素分离中的研究现状及趋势,并展望了溶剂萃取法在锂同位素分离和未来青海、西藏盐湖锂资源高值化利用中的潜在应用前景。     

某电站尾调室顶拱喷层平行轴向开裂缝原因分析探讨

根据素描及实际开挖揭露地质情况,对尾调室工程地质概况、开挖揭示的地质条件、主要工程地质问题以及尾调室顶拱喷层裂缝的情况进行了介绍; 从施工因素、地质因素、地应力因素、温度因素、松弛圈因素、喷护接缝、受力不均等方面对顶拱平行轴向开裂缝原因进行了分析探讨,认为结构面因素和地应力因素是主要原因,爆破扰动及支护不及时为诱因,围岩破坏为应力控制型破坏和块体控制型破坏相结合。     

运用神经网络识别注射过金属离子溶液树冠的实验研究

本文运用神经网络ＢＰ算法对高分辨率航空多光谱图像进行了模式识别研究,成功地识别出注射过金属离子溶液树冠,并与最大似然法在分类结果进行比较。得出在分类精度上,神经网络模式识别比传统的最大似然分类方法具有优势的结论。     

Application of 3D triangulations of airborne laser scanning data to estimate boreal forest leaf area index

We propose 3D triangulations of airborne Laser Scanning (ALS) point clouds as a new approach to derive 3D canopy structures and to estimate forest canopy effective LAI (LAI_e). Computational geometry and topological connectivity were employed to filter the triangulations to yield a quasi-optimal relationship with the field measured LAI_e. The optimal filtering parameters were predicted based on ALS height metrics, emulating the production of maps of LAI_e and canopy volume for large areas. The LAI_e from triangulations was validated with field measured LAI_e and compared with a reference LAI_e calculated from ALS data using logarithmic model based on Beer’s law. Canopy transmittance was estimated using All Echo Cover Index (ACI), and the mean projection of unit foliage area (β) was obtained using no-intercept regression with field measured LAI_e. We investigated the influence species and season on the triangulated LAI_e and demonstrated the relationship between triangulated LAI_e and canopy volume. Our data is from 115 forest plots located at the southern boreal forest area in Finland and for each plot three different ALS datasets were available to apply the triangulations. The triangulation approach was found applicable for both leaf-on and leaf-off datasets after initial calibration. Results showed the Root Mean Square Errors (RMSEs) between LAI_e from triangulations and field measured values agreed the most using the highest pulse density data (RMSE = 0.63, the coefficient of determination (R²) = 0.53). Yet, the LAI_e calculated using ACI-index agreed better with the field measured LAI_e (RMSE = 0.53 and R² = 0.70). The best models to predict the optimal alpha value contained the ACI-index, which indicates that within-crown transmittance is accounted by the triangulation approach. The cover indices may be recommended for retrieving LAI_e only, but for applications which require more sophisticated information on canopy shape and volume, such as radiative transfer models, the triangulation approach may be preferred.     

冠醚/离子液体体系对锂离子萃取动力学的研究

本文通过恒界面池法研究了以4’—乙酰基苯并—15—冠—5作为萃取剂和1—丁基—3—甲基咪唑双[(三氟甲基)磺酰基]酰亚胺作为协萃剂的萃取体系从高浓度水溶液中提取锂的动力学。研究了搅拌速度、平衡时间、温度、界面面积和传质阻力区对锂离子传质速率的影响。结果表明,界面膜的厚度在1 600 rpm~2 000 rpm 转速范围内是逐渐变薄的,并且在1 800 rmp~2 000 rmp转速范围内是没有变化的,说明锂离子传质速率1 800 rmp~2 000 rmp转速范围内是不变的;在锂离子的萃取平衡时间为40 min;萃取过程的传质阻力主要来自有机相;该萃取过程是混合控制的动力学过程;在两相界面上发生的萃取反应。通过研究锂离子、冠醚离子液体的浓度,锂离子的动力学方程可表达为:νLi,0=10-3.843±0.001·[Li⁺]⁰.907 1·[⁺] 0.832 8·[AcB15C5] 0.855 5。通过两相界面处形成锂离子最终配合物的传质速率步骤推导出锂的提取机理,这与实验结果一致。     

Crown foliage dynamics of mangrove <Emphasis Type="Italic">Kandelia obovata</Emphasis> in Manko Wetland,Okinawa Island,Japan

The crown foliage dynamics of Kandelia obovata (S., L.) Yong were investigated, including leaf recruitment, survival and leaf growth. Newly flushed leaves occurred successively throughout the year, with a maximum in July and a minimum in January. The highest leaf death was in August, whereas it was the lowest in January. The relative mortality rate of leaves seemed to depend on the season when new leaves flushed. The growth pattern of leaves varied among seasons. The maximum leaf area was significantly larger in winter than in autumn, but showed no significant difference between the winter and the other seasons. The half-expansion period and the intrinsic rate of increase were respectively longer and lower in winter than in the other seasons. Therefore, leaves flushed in summer grew faster in their initial stage and attained their maximum leaf area sooner than those flushed in winter. This most likely results from the difference in temperature between summer and winter. The crown leaf area was almost stable throughout the year, as if homeostatic control is likely to function. Stipule litterfall decreased significantly with increasing flower and propagule litterfalls, indicating that a high production of flowers and propagules results in low leaf recruitment. This may be because flower production and propagule growth impose a severe burden on K. obovata.     

三峡水利枢纽地下电站主厂房施工期顶拱围岩块体研究

对于大跨度地下洞室,顶拱围岩的稳定关系施工过程顺利和安全。三峡地下电站主厂房围岩为裂隙化硬质岩体,开挖后易产生块体,对局部围岩稳定不利。依据顶拱分部分序开挖支护过程,采用信息化施工地质工作流程,运用三维块体分析程序GeneralBlock,对开挖揭露断裂结构面组合构成块体进行快速搜索定位和稳定性分析,及时指导顶拱支护设计和施工。研究结果为:顶拱揭露可动块体43个,其中有11个为不稳定块体,16个为潜在不稳定块体,需及时加固处理。     

Stability of reef framework and post settlement mortality as the structuring factor for recovery of Malakal Bay Reef,Palau, Micronesia: 25 years after a severe COTS outbreak

Corals in Malakal Bay reefs were devastated in the 1979 Crown of Thorns Starfish (COTS) outbreak. It has been almost 30 years since the outbreak and coral cover at the study sites have not come close to the cover before the outbreak. A question is asked: what factors may contribute to the slow recovery of these reefs: recruitment or post-settlement mortality? Two habitat types within the reef systems were monitored using coral transplants to determine if corals can survive in these environments and recruitment tiles to see if there are larvae coming into the system. The study revealed that coral survivorship is high in the fore reef areas compared to the reef channel slopes and that larvae is not a limiting factor to natural recovery. Stability of the reef framework, i.e. unstable rubble substrate, and possibly high post settlement mortality, are the structuring factors that determine the recovery process in these reef systems and possibly so for similar habitats in other reef systems throughout Palau.     

Individual tree crown segmentation in tropical peat swamp forest using airborne hyperspectral data

Abstract

Individual tree crown segmentation is important step for deriving various information for fine-scale analysis of ecological process. However, only several studies have applied tree crown segmentation in tropical forest ecosystems, especially in mixed peat swamp forests. In this study, hyperspectral data were used to detect changes in the biochemical and biophysical characteristics, which are important factors for tree crown segmentation. Principal Component Analysis method was performed to investigate its influence on crown segmentation. Visually Selected PCs, 160 PCs and 160 Spectral Bands image were used and two segmentation techniques; Watershed Transformation and Region Growing segmentation were applied on those images. The highest accuracy was achieved for the crown segmentation is using Region Growing segmentation, based on 1:1 measurement, D value and RMSE value. The results obtained from 160 PCs image using region growing algorithm shows better accuracy with D value of 0.2 (80% accuracy, 20% error) and RMSE of 9.9 m².