三维激光测量技术在大型复杂钢结构工程建造中的应用     

祝明然 《测绘通报》2019,(8):92-95

以山东第一高楼云鼎大厦建造过程为例，对三维激光扫描技术应用于大型复杂钢结构工程建造中的关键技术进行了研究。通过对大型复杂钢结构部件进行三维激光扫描，并与BIM预制模型比对，事先检测钢构件加工误差，提出了大型复杂钢结构部件误差检测关键技术流程，实现了高精度特征误差统计，为大型复杂钢结构工程智能建造提供了有效先进的检测、监测手段，具有较大的借鉴及实用价值。  相似文献   

国家应急测绘保障能力建设项目总体技术设计   总被引：2，自引：1，他引：1  

赵勇  武昊  王中祥  朱杰 《测绘通报》2019,(9):121-127

我国是自然灾害多发国家，给人们生命、财产安全造成了极大威胁。应急测绘是我国突发事件应急体系和综合防灾减灾工作体系的重要组成部分。近年来，应急测绘装备和技术水平取得了巨大进展，构建规模化、协同化、覆盖全国的应急测绘保障能力已成为应急测绘保障工作的必然趋势。本文针对应急测绘保障工作的特点，分析了应急测绘业务流程和数据流程，提出了国家应急测绘保障能力建设的总体架构、建设内容设计和系统接口设计，讨论了项目建设的预期效果和下一步努力方向。相关研究可为进一步做好应急测绘保障工作的顶层设计、加强科学统筹工作奠定基础。  相似文献   

Climate moderates potential shifts in streamflow from changes in pinyon‐juniper woodland cover across the western U.S.          下载免费PDF全文

Ryan J. Niemeyer  Timothy E. Link  Robert Heinse  Mark S. Seyfried 《水文研究》2017,31(20):3489-3503

Pinyon‐juniper (PJ) cover has increased up to 10‐fold in many parts of the western U.S. in the last 140+ years. The impacts of these changes on streamflows are unclear and may vary depending on the intra‐annual distribution and amount of precipitation. Given the importance of streamflow in the western U.S., it is important to understand how shifts in PJ woodland cover may produce changes in streamflow across the region's diverse hydroclimates. To this end, we simulated the land surface water balance with contrasting woodland and grassland cover with the Hydrologiska Byråns Vattenbalansavdelning (HBV) model at a 4‐km resolution across the distribution of PJ woodlands in the western U.S. We used shifts in evapotranspiration (ET) between woodland and grassland cover as a proxy for potential changes in streamflows. Comparison of HBV model results with paired catchment studies indicated the model reasonably simulated annual decreases in ET with changes from woodland to grassland cover. For the northern and western ecoregions of the PJ distribution in the western U.S. where precipitation predominantly occurs in the winter, HBV simulated a 25 mm (37%) annual decrease in ET with conversion to grassland from woodland. Conversely, in southern ecoregions of PJ distribution with prominent summer monsoons, annual differences in ET were only 6 mm (19%). Our results suggest that only 29% of the PJ distribution, compared to an estimated 45% based on precipitation amount alone, has the potential for meaningful increases in streamflow with land cover change from woodland to grassland.  相似文献   

三维激光扫描技术在建筑立面测绘中的应用     

张立  宋莉 《测绘通报》2019,(9):152-154

针对传统建筑立面测量方法作业效率低下问题，笔者探索出基于三维激光扫描技术快速实现建筑立面测绘的应用方案。本文结合实际场景，通过天宝TX8激光扫描仪获取建筑点云数据，利用Trimble RealWorks软件进行点云绘图。结果表明，地面激光扫描技术可以高效地实现建筑立面测绘，具有一定的推广意义。  相似文献   

Sensitivity analysis applied to finite element method model for coupled multiphase system     

R. Ngaradoumbe Nanhorngué  F. Pesavento  B.A. Schrefler 《国际地质力学数值与分析法杂志》2013,37(14):2205-2222

Today multiphysics problems applied to various fields of engineering have become increasingly important. Among these, in the areas of civil, environmental and nuclear engineering, the problems related to the behaviour of porous media under extreme conditions in terms of temperature and/or pressure are particularly relevant. The mathematical models used to solve these problems have an increasing complexity leading to increase of computing times. This problem can be solved by using more effective numerical algorithms, or by trying to reduce the complexity of these models. This can be achieved by using a sensitivity analysis to determine the influence of model parameters on the solution. In this paper, the sensitivity analysis of a mathematical/numerical model for the analysis of concrete as multiphase porous medium exposed to high temperatures is presented. This may lead to a reduction of the number of the model parameters, indicating what parameters should be determined in an accurate way and what can be neglected or found directly from the literature. Moreover, the identification parameters influence may allow to proceeding to a simplification of the mathematical model (i.e. model reduction). The technique adopted in this paper to performing the sensitivity analysis is based on the automatic differentiation (AD), which allowed to develop an efficient tool for the computation of the sensitivity coefficients. The results of the application of AD technique have been compared with the results of the more standard finite difference method, showing the superiority of the AD in terms of numerical accuracy and execution times. From the results of the sensitivity analysis, it follows that a drastic simplification of the model for thermo‐chemo‐hygro‐mechanical behaviour of concrete at high temperature, is not possible. Therefore, it is necessary to use different model reduction techniques in order to obtain a simplified version of the model that can be used at industrial level. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

Interactions between a cyanobacterial bloom (<Emphasis Type="Italic">Microcystis</Emphasis>) and the submerged aquatic plant <Emphasis Type="Italic">Ceratophyllum oryzetorum</Emphasis> Kom.     

李敦海  李根保  陈武雄  刘永定 《中国海洋湖沼学报》2009,27(1):38-42

In aquatic ecosystems, macrophytes and phytoplankton are main primary producers, in which macrophyte plays an important role in maintaining clear water state, while phytoplankton often dominates in turbid waterbodies. In the present study, the growth and photosynthetic activity of the submerged aquatic plant Ceratophyllum oryzetorum Kom. in different cell densities of cyanobacterial bloom are studied. The results show that the plant length and fresh mass of C. oryzetorum are promoted by low cyanobacterial cell densities. Medium and high cyanobacterial cell densities, on the contrary, act as inhibitory. Furthermore, the photosynthetic activity of C. oryzetorum is strongly inhibited by high cyanobacterial cell densities. To a certain extent, the growth of cyanobacteria is inhibited by C. oryzetorum, but no significant effect is found in this study. Supported by the Innovation Project of CAS (No.KZCX2-YW-426), a Provincial Project of Hubei (No. 2006AA305A0402) and the National Basic Research Program of China (973 Program, No. 2002CB 412306)  相似文献   

Species diversity and population status of threatened plants in different landscape elements of the Rohtang Pass,western Himalaya     

K. N. Singh  Gopichand  Amit Kumar  Brij Lal  N. P. Todaria 《山地科学学报》2008,5(1):73-83

This paper highlights the quantitative estimates of plant species diversity and ecosystems of the Rohtang Pass,which is one of the most preferred visiting spots by tourists in Himachal Pradesh （H.P.）,India. In spite of high pressure of anthropogenic activities,the Rohtang Pass still harbours a variety of flowering plants with economic value,including various medicinal herbs. In order to observe species diversity in different landscape elements （LSEs）,ground surveys were conducted in nine unique LSEs within the elevation range between 3624 m and 4332 m. Plant community structure in each LSE was studied using stratified random sampling where a total 56 quadrats of 1 m^2 in size for herbs and 7 quadrats of 25 m^2 for shrubs were made. Of the total 50 plant species belonging to 15 families recorded in different random quadrats,24 species were found of medicinal value. Maximum species richness （18） and value of Shannon diversity （H＇=2.2648） were observed on northeast-facing slope in Picrorhiza kurrooa dominated LSE in moist area,followed by Rheum emodi LSE （species richness = 17 and H＇ = 2.4141） distributed on south-facing slope. Maximum values of species richness and Shannon diversity in Rheum emodi LSE were observed between 8 ～ 12 and 1.4797 ～ 2.1911,respectively. Rhododendron anthopogon dominated LSE on northwest-facing slope was found least diverse in terms of species richness where the Simpson index of dominance （D） was 0.4205. The species were equal in abundance in P. kurrooa LSE on east-facing slope and Pleurospermum candollii LSE on north-facing slope,showing the maximum similarity in terms of species distribution between the two LSEs. Low turnover of species across common LSEs gives an idea regarding their limited distribution. Five species of threatened category according to the IUCN criteria were observed in seven LSEs. The largest population of threatened medicinal plants was recorded on northeast and northwest-facing slopes where population density of Bergenia stracheyi （  相似文献   

Late Quaternary environments,vegetation and agriculture in northern New Zealand     

M. Horrocks  S. L. Nichol  P. C. Augustinus  I. G. Barber 《第四纪科学杂志》2007,22(3):267-279

A sedimentological and plant microfossil history of the Late Quaternary is preserved in two sediment cores from early Polynesian ditch systems on southern Aupouri Peninsula. The study places human activities into a geomorphological and ecological context and allows comparison of natural and anthropogenic effects on two different geological settings: a floodplain and a relatively closed peat swamp. The data fill part of the current gap in the environmental record from northern New Zealand, namely MIS 3 (57k–26k yr BP). There is evidence for an increase in fire frequency in the region after 40k ¹⁴C yr BP, suggesting a shift to drier (and cooler) conditions. Pollen records show that conifer‐hardwood forest dominated by podocarps (especially Dacrydium) prevailed prior to Polynesian arrival and deforestation within the last millennium, with Fuscopsora insignificant throughout. Both cores show sections with gaps in deposition or preservation, possible flood‐stripping of peat during the pre‐Holocene and mechanical disturbance by early Polynesians. The identification of prehistoric starch grains and other microremains of introduced Colocasia esculenta (taro) in both cores supports indirect evidence that the ditch systems of far northern New Zealand were used for the extensive cultivation of this crop. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

A note on the generation of periodic granular microstructures based on grain size distributions     

H. A. Meier  E. Kuhl  P. Steinmann 《国际地质力学数值与分析法杂志》2008,32(5):509-522

This short communication discusses an algorithm suited for the generation of periodic microstructures of granular media. Its particular features are a user‐defined grain size distribution, a representative volume element which is intrinsically periodic ab initio and a user‐defined termination criterion, controlled by an increase of volume fraction. For low densities our particle packings resemble fluids or gases, while we aim to reach for rather dense particle packings, similar to granular solids. The generated microstructures can thus be readily incorporated into large multiscale simulations, e.g. on the integration point level of a finite element analysis of a particular sand or concrete. The individual grain size distribution of the granular medium is incorporated through the introduction of different growth rates governing the final particle size distribution. We briefly sketch the generation of the representative volume element within a serial event‐driven scheme and demonstrate how periodic boundary conditions are ensured throughout the representative volume element generation process. The potential of the suggested algorithm will be illustrated through the generation of two different periodic multi‐disperse microstructures. They are based on different given grain size distributions, one for a quartz sand with a low non‐uniformity index and one for concrete aggregates classified as A32 by the German standard norm DIN 1045 to have a rather large variation in grain size. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

Assessment of diversity, distribution, conservation status and preparation of management plan for medicinal plants in the catchment area of parbati hydroelectric project stage — III in Northwestern Himalaya   总被引：1，自引：1，他引：0  

S. S. Samant  Jitendra S. Butola  Aman Sharma 《山地科学学报》2007,4(1):034-056

The developmental activities, particularly the construction of hydroelectric projects are causing a great loss of biodiversity in the Indian Himalayan Region. The Himachal Pradesh, a part of IHR is well known for the development of hydroelectric projects. The Parbati H.E. Project is amongst the major projects of the State. The different stages of the project are all causing loss of biodiversity of the area. Stage III of the Parbati H.E. Project is a run of the river scheme on the Sainj River downstream of Power House of Parbati H.E. Project Stage II. The project shall utilize regulated discharge of Parbati H.E. Project Stage II and inflow of River Sainj for power generation, and has been contemplated as a peaking station operating in tandem with Stage II. The present study has been undertaken to see the impact of hydroelectric project on the biodiversity, particularly on medicinal plants. A total of 104 species of medicinal plants, belonging to different life forms, i.e., trees (23 spp.), shrubs (22 spp.), herbs (57 spp.) and ferns (2 spp.) were recorded. The species have been analyzed and studied for their distribution, classification, altitudinal zones, part (s) used, indigenous uses, nativity, endemism and rarity. DDifferent parts of these species, such as whole plants, roots (including rhizomes and tubers), leaves, flowers, fruits, seeds, stems, barks, spikes, nuts and insect galls are used by the inhabitants for curing various diseases and ailments. 30 species are native to the Himalayan region, 9 species native to the Himalayan region and adjacent countries also and 65 species are non-natives. 9 species are near endemics. Considering the whole Himalaya as a biogeographic unit (sensu lato), the near endemics are endemic to the Himalaya. Among these species, Zanthoxylum armatum is categorized as Endangered and Valeriana wallichii as Vulnerable. Hedychium spicatum, Rhus javanica, Berberis lycium, Thalictrum foliolossum, Salvia lanata, Rubia cordifolia and Bergenia ligulata may be considered as threatened species due to their over exploitation for trade. 90 species are propagated by seeds, 8 species by seeds and rhizomes/roots/tubers, 4 species by seeds and cuttings, and 2 species by sori. A management plan for the cultivation and conservation of the medicinal plants in the dam submergence area, and the commercially viable medicinal plants with high value in the catchment area is suggested.  相似文献