基于机载LiDAR数据的建筑物轮廓提取

建筑物轮廓作为建筑物三维重建的重要元素,在建立智慧城市和数字城市中至关重要。本文针对从机载激光雷达点云中提取建筑物轮廓数据处理的点云滤波、建筑物屋顶面提取、建筑物轮廓提取,以及提取精度评定各环节存在的一些问题,提出了一种综合区域生长改进算法、三维Hough变换算法和α-shape算法的建筑物轮廓提取方法。该方法在对机载LiDAR点云数据去噪的基础上,首先利用改进的区域生长算法滤波地面点,并基于地物点到地面的归一化高程特征通过高度阈值去除高度较为低矮的地物点;再基于三维Hough变换算法从剩余建筑物和高大树木点云中提取建筑物平面;最后使用α-shape算法提取建筑物的轮廓信息。对使用RIEGLVQ-1560i机载激光雷达测量系统扫描的某城区点云数据进行计算,通过匹配度、形状相似度和位置精度等评价指标对提取的建筑物轮廓进行精度评定。结果表明,综合区域生长改进算法、三维Hough变换算法和α-shape算法的建筑物轮廓提取方法可以准确提取建筑物的轮廓信息,对于大范围的建筑物轮廓提取具有稳定性和普遍适用性。     

一个新的来自于弧菌QD-5并具有Poly-G内切功能的褐藻胶裂解酶的克隆和性质表征

Seven bacterial clones with alginate-utilizing activity were isolated from rotten kelp. By activity test, the Vibrio sp.QD-5 with the potential alginate-degrading capability was chosen to carry out the draft genome sequencing, and the result showed that the Vibrio sp. QD-5 containing an alginate lyase gene cluster. One of these genes, aly-IV,was cloned and characterized for the first time. After overexpression, Aly-IV, with a molecular mass of about62 kDa and a theoretical isoelectric point(pI) of 5.12, was purified to a specific activity of 1 256.78 U/mg and showed highest activity at 35°C in the Tris-HCl buffer at pH of 8.9. Moreover, the enzyme activity was enhanced by the metal ions of Na~+, K~+ and Mg~(2+) under certain concentration. Aly-IV degraded favorably polyG blocks in an endo-type, yielding monomer and dimer as the main products. Due to its high substrate specificity, Aly-IV could be used as a potential tool for production of polyG oligosaccharides with low degree of polymerization(DP) and for determining the fine structure of alginate.     

Immunotoxicity Effect of Benzo[α]Pyrene on Scallop Chlamys f arreri

The toxic effects of benzo[α]pyrene （B[α]P） at different concentrations （0.1, 0.5, 1, 2.5 and 7.5 μgL^-1） on scallop （Chlamys farreri） immune system were studied. The results showed that B[α]P had significant toxic effects on the haemocyte counts, neutral red uptake, phagocytosis, bacteriolytic and antibacterial activity （P〈0.05）, while the seawater control and acetone control had no significant differences. The haemocyte counts, neutral red uptake, phagocytosis and bacteriolytic activity in all B[α]P treatment groups as well as antibacterial activity in groups of 0.5, 1, 2.5 and 7.5 μgL^-1·B[α]P decreased significantly （P〈0.05）. Some of these indices tended to be stable on the sixth day and others on the ninth day, and the indices showed clear time- and concentration-response to B[α]E Bactenolytic activity in 0.1 μgL^-1 B[α]P treatment group and antibacterial activity in 0.1 ggLl and 0.5 μgL^-1 B[α]P treatment groups increased at the beginning of exposure and reached their peaks on day 1 and day 6, respectively. Following that, both activities decreased gradually and became stable after day 9. When all the indices reached stability, they were significantly lower than those in control group （P〈0.05）, except for antibacterial activity in 0.1 μgLl B[α]P treatment group （P〉0.05）. Thus, B[α]P has evident toxic effects on scallop immune system, which supports the view that a relationship exists between pollution and lmmunomodulation in aquatic organisms.     

Vitellogenin as biomarker for estrogenicity in flounder Platichthys flesus in the field and exposed to 17α-ethinylestradiol via food and water in the laboratory

The ability of 17α-ethinylestradiol (EE2) to elevate vitellogenin levels were investigated in male flounder Platichthys flesus and vitellogenin concentrations in flounders from the Danish coastal environment were determined. Male flounders were exposed to 17α-ethinylestradiol (EE2) via food or water. Average vitellogenin concentrations in the control fish ranged between 25 and 100 ng mL⁻¹. Exposure to 5.1, 8.1 and 16.8 ng EE2 L⁻¹ in water and 500 and 5000 ng EE2 kg⁻¹ body weight (bw) every second day in the food increased the plasma vitellogenin concentration in a concentration and time dependent manner, whereas exposure to 2.7 ng EE2 L⁻¹ in water for 21 d and 5 and 50 ng EE2 kg⁻¹ bw for 12 days in the food did not. EE2 could be detected in liver and testes (but not in muscle) after exposure to 8.1 and 16.8 ng EE2 L⁻¹ in the water and 5000 ng EE2 kg⁻¹ bw in the food; the highest concentration was 6 ng g⁻¹ wet weight in liver. The majority of the male flounders collected from nine coastal Danish sites from 1999 to 2004 had vitellogenin concentrations below 100 ng mL⁻¹, and only at two sites moderate estrogenic inputs were indicated.     

A modal α2-dynamo in the limit of asymptotically small viscosity

Abstract

A spherical α²-dynamo is presented as an expansion in the free decay modes of the magnetic field. In the limit of vanishing viscosity the momentum equation yields various asymptotic expansions for the flow, depending on the precise form of the dissipation and boundary conditions applied. A new form for the dissipation is introduced that greatly simplifies this asymptotic expansion. When these expansions are substituted back into the induction equation, a set of modal amplitude equations is derived, and solved for various distributions of the α-effect. For all choices of α the solutions approach the Taylor state, but the manner in which this occurs can vary, as previously found by Soward and Jones (1983). Furthermore, as hypothesized by Malkus and Proctor (1975), but not previously demonstrated, the post-Taylor equilibration is indeed independent of the viscosity in the asymptotic limit, and depending on the choice of a may be either steady-state or oscillatory.     

Parity coupling in α2-dynamos

Abstract

The modal α²-dynamo of Hollerbach and Ierley (1991) is extended to include both parities, dipolar and quadrupolar. Two choices of α are considered. As before, the solutions approach the Taylor state, and the subsequent equilibration is independent of the viscosity in the asymptotic limit. The first choice of α yields stable steady-state pure-parity solutions of either type, and may yield some insight into the question of parity selection. The second choice of α yields rather complex time-dependent mixed-parity solutions, and demonstrates the extent to which parity coupling can affect the evolution of time-dependent solutions.     

Algal diets and natural xenobiotics impact energy allocation in cladocerans. I. Daphnia magna

Recently emerged indications imply that particular concentrations and qualities of dissolved organic carbon (DOC) have the potential to reduce species diversity in zooplankton. In this contribution, we tested the impact of a major component of DOC, the dissolved humic substances (HSs), on two life history traits of a clone of Daphnia magna, namely lifespan and reproduction. We chose reproduction as a variable since it guarantees the persistence of the population in its habitat, and lifespan was selected as the most integrative individual variable. We found that lifespan was extended by exposure to HSs, but lifetime reproduction was clearly reduced. On the other hand, the mineral and biochemical composition of food also significantly modulated these life history traits. By feeding coccal green algae that contained linolenic acid, arginine (Arg), and histidine (His), but that lacked polyunsaturated fatty acids (PUFAs) with C-back bones >18, we examined how short-chained PUFAs, either alone or in concert with Arg and His, are able to modulate life history traits. Our expectation was that the additional challenge by HSs would shift the energy allocation in favor of reproduction. We found that the carbon and amino acid content may account for longevity, even when challenged by HSs. Reproduction appeared to be triggered by the C:P and N:P ratios of the food, particularly given the rather low P-content, which was within the range of severe growth limitation. Consequently, exposure to HSs reduced offspring numbers. Resting eggs without males occurred only in Desmodesmus armatus fed Daphnia that were simultaneously exposed to HSs. Under these conditions, the total amino acid (AA) content seemed to trigger reproduction. In summary, exposure to HSs appeared to have the potential to change the competitive ability of zooplankters by modulating the energy allocation between body maintenance and reproduction.     

一种利用Cloude-Pottier分解和极化白化滤波的全极化SAR图像分类算法

提出了一种新的基于Cloude-Pottier分解和极化白化滤波(PWF)的全极化SAR数据分类算法。该算法利用PWF的结果来代替反熵A对复WishartH/α分类结果进行进一步细化,按PWF的值将复WishartH/α分类结果由8类分为16类,然后再次进行Wishart迭代分类。实验结果表明,该算法能有效地提高分类精度,分类结果明显优于常规的复WishartH/α分类结果和复WishartH/α/A分类结果。     

Horton定律及分枝网络结构的分形描述

在Horton定律的基础上提出分枝网络结构的端头构成的集合的分形维数更具有实际意义,并得出了端头集合的自相似维数。在此基础上,又给出了具有两个不同分枝长度比的两分枝结构的端头的多分形描述,并定性地分析了其f(α)～α谱和Dq～q谱。讨论了其在实际河流网络中的意义。