基于加权约束的单体建筑物点云表面重建算法

建筑物点云表面重建在高精度城市测绘、虚拟现实等领域有十分广泛的应用前景。由于建筑物的几何形态多变,重建算法普遍存在计算速率慢、拟合精度低和模型结构不完整的问题。为此,本文以单体建筑物为研究对象,提出基于加权约束的单体建筑物点云表面重建算法,在表面初始化过程中充分考虑数据对结构拟合的贡献。在此基础上,构建基于正则集的单体建筑物表面重建算法,实现建筑物拟合过程中的加权拟合误差、近邻结构平滑的同步优化。针对多类建筑物三维点云的实验结果表明,相比传统的建筑物重建策略,本文的加权约束方法可根据不同类型的点云数据设计自适应权重,并选择模型拟合中最优的权重函数,在高噪声、低精度点云数据下能得到更高精度的单体建筑物表面模型。     

鲈鱼的鳃寄生车轮虫病及扫描电镜观察

报道鲈鱼的鳃寄生车轮虫病及病理组织的扫描电镜观察。病原鉴定为 :直钩车轮虫、杜氏车轮虫、日本车轮虫、劳牧小车轮虫及简单两分虫 5种车轮虫科纤毛虫 ,其中数量上占优势的为直钩车轮虫。扫描电镜观察结果表明 ,鳃寄生车轮虫可对宿主的上皮组织产生明显的机械性损伤并造成鳃丝粘液分泌增多及炎症反应。文中就海水养殖鱼类及野生鱼类由车轮虫寄生造成的危害及防治途径做了探讨。     

微分算子展开与耦合势三维有限体积法快速计算随钻超深前视电阻率测井响应非线性Born逼近

本文将非均质各向异性地层中电磁场耦合势Helmhotz方程分解为各向异性背景场方程与散射场方程,并应用算子展开技术推导出耦合势Born级数解,建立一套三维非均质各向异性地层中随钻超深前视电阻率测井响应各阶散射电磁场与非线性Born逼近的有效计算方法.首先,利用传输线法与二维插值技术确定背景电磁场空间分布,得到零阶Born逼近解,然后根据电磁场耦合势的Born级数解推导出各阶散射电磁场方程与递推关系,通过三维有限体积法实现各阶散射场耦合势方程的离散,在此基础上结合MKL PARDISO并行技术,通过递推方式逐步计算各阶散射电磁场,并根据Born级数部分和确定不同阶次的非线性Born逼近.最后利用数值模拟结果对正演算法加以检验,并深入研究分析各阶散射场的变化特征与Born级数的收敛性质.

     

城市生态环境分区遥感综合分析--以贵阳市城区为例

建设环境良好的城市是人居环境应用研究的重点领域。而人居环境的研究则涉及到宏观和中、微观层次,是自然生态系统和人工生态系统的结合。在建设可持续发展的人居环境的过程中,遥感、地理信息系统、全球定位系统技术对空间数据和属性数据处理、管理、分析可以发挥积极的作用。本文以贵阳市城区为例,探讨了"3S"技术在人居环境研究中城市生态环境分析,以期对贵阳市城市规划提出具体的改进建议,使之更符合建设良好的人居环境的要求。     

黄河三角洲滨海地区植物生长季大气氮沉降动态

利用SCJ-302型降水降尘自动采样器在植物生长季对黄河三角洲滨海湿地的大气氮沉降进行监测,对沉降物中水溶性离子、干、湿沉降氮输入量、铵态氮和硝态氮在总沉降量中的贡献率及月变化动态等分析表明：黄河三角洲植物生长季,大气干、湿沉降中SO₄^2-和NO₃^-占阴离子总量的92%以上,和Na⁺和Ca²⁺占阳离子总量的80%以上,总N沉降量约为2 264.24 mg/m²,且69%集中在降雨量较丰沛的6-8月。其中干沉降氮贡献率约为32.02%,主要集中在春季。N的湿沉降量与降雨量呈显著正线性相关（R²=0.82）,在降雨量丰沛的8月,达到最大值675.64 mg/m²。该地区大气干沉降的氮素形态以硝态氮为主,约占氮素输入量的57.21%,湿沉降中以铵态氮为主,约占氮素输入量的56.51%。植物生长季中,大气沉降中的硝态氮与铵态氮含量对表层10 cm土壤的月平均贡献率分别为约31.38%和20.50%,可见大气氮沉降是黄河三角洲滨海区域土壤主要氮素来源之一。     

山东长岛黄土沉积物的磁性与碳酸盐特征及其环境意义初探

通过对长岛沉积物采样和磁性测试,分析和讨论了长岛黄土沉积物的磁性特征:该剖面磁性矿物的含量并不是很高,且以亚铁磁性矿物为主,磁性矿物的粒度主要以细粒为主,亚铁磁性矿物的变化在沉积物磁性变化中占主导地位.通过对沉积物磁性特征和碳酸盐特征的对比发现:该剖面沉积物磁化率和碳酸盐具有很好的对应关系,并且明显表现出4个阶段的主要变化,对应了暖湿和冷干的气候旋回.根据沉积物的磁化率与古气候环境的内在联系,结合碳酸盐含量变化情况,对该地区风成沉积物的物源变迁及环境演变也进行了初步探讨和分析.     

城乡结合部土地利用变化的信息提取技术与分析--以无锡市为例

作为两种截然不同的生态系统过渡区,城乡结合部是土地利用/土地覆被变化最激烈地区之一,城乡结合部的土地利用情况日益受到人们重视.本文以无锡市为例,利用3S技术提取城乡结合部的范围和土地利用/土地覆被状况信息,提出了确定无锡市城乡结合部范围边界的半自动提取模型和结合部土地利用类型半自动提取模型,并对无锡市城乡结合部土地利用结构及其变化进行分析,揭示了无锡市城乡结合部土地利用/土地覆被变化特征,据此提出城乡结合部土地合理利用的建议.     

城市地下空间开发利用容量评估的基础研究

该文探讨了城市地下空间开发利用容量评估的必要性,容量评估研究的基本内容及其关键技术。指出当前城市地下空间容量评估基础研究包括指标体系、评估模型、评估平台与评估示范四方面。城市地下空间容量评估研究不仅有利于城市地下空间的合理利用和有序开发,也有利于引导城市地面设施的合理布局与科学规划,对保障现代城市的可持续发展具有重要意义。     

The nature of the hard state of Cygnus X-3

The X-ray binary Cygnus X-3 (Cyg X-3) is a highly variable X-ray source that displays a wide range of observed spectral states. One of the main states is significantly harder than the others, peaking at ∼20 keV, with only a weak low-energy component. Due to the enigmatic nature of this object, hidden inside the strong stellar wind of its Wolf–Rayet companion, it has remained unclear whether this state represents an intrinsic hard state, with truncation of the inner disc, or whether it is just a result of increased local absorption. We study the X-ray light curves from RXTE /ASM and CGRO /BATSE in terms of distributions and correlations of flux and hardness and find several signs of a bimodal behaviour of the accretion flow that are not likely to be the result of increased absorption in a surrounding medium. Using INTEGRAL observations, we model the broad-band spectrum of Cyg X-3 in its apparent hard state. We find that it can be well described by a model of a hard state with a truncated disc, despite the low cut-off energy, provided the accreted power is supplied to the electrons in the inner flow in the form of acceleration rather than thermal heating, resulting in a hybrid electron distribution and a spectrum with a significant contribution from non-thermal Comptonization, usually observed only in soft states. The high luminosity of this non-thermal hard state implies that either the transition takes place at significantly higher   L / L _E  than in the usual advection models, or the mass of the compact object is  ≳20 M_⊙  , possibly making it the most-massive black hole observed in an X-ray binary in our Galaxy so far. We find that an absorption model as well as a model of almost pure Compton reflection also fit the data well, but both have difficulties explaining other results, in particular the radio/X-ray correlation.     

The star-forming content of the W3 giant molecular cloud

We have surveyed a ∼0.9 square degree area of the W3 giant molecular cloud (GMC) and star-forming region in the 850-μm continuum, using the Submillimetre Common-User Bolometer Array on the James Clerk Maxwell Telescope. A complete sample of 316 dense clumps were detected with a mass range from around 13 to  2500 M_⊙  . Part of the W3 GMC is subject to an interaction with the H  ii region and fast stellar winds generated by the nearby W4 OB association. We find that the fraction of total gas mass in dense, 850-μm traced structures is significantly altered by this interaction, being around 5–13 per cent in the undisturbed cloud but ∼25–37 per cent in the feedback-affected region. The mass distribution in the detected clump sample depends somewhat on assumptions of dust temperature and is not a simple, single power law but contains significant structure at intermediate masses. This structure is likely to be due to crowding of sources near or below the spatial resolution of the observations. There is little evidence of any difference between the index of the high-mass end of the clump mass function in the compressed region and in the unaffected cloud. The consequences of these results are discussed in terms of current models of triggered star formation.