Academic literature on the topic 'Sea/Land Transition identification'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the lists of relevant articles, books, theses, conference reports, and other scholarly sources on the topic 'Sea/Land Transition identification.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Journal articles on the topic "Sea/Land Transition identification"
1
Luppichini, Marco, Monica Bini, Marco Paterni, Andrea Berton, and Silvia Merlino. "A New Beach Topography-Based Method for Shoreline Identification." Water 12, no. 11 (November 5, 2020): 3110. http://dx.doi.org/10.3390/w12113110.
Full textAbstract:
The definition of shoreline is not the same for all contexts, and it is often a subjective matter. Various methods exist that are based on the use of different instruments that can determine and highlight a shoreline. In recent years, numerous studies have employed photogrammetric methods, based on different colours, to map the boundary between water and land. These works use images acquired by satellites, drones, or cameras, and differ mainly in terms of resolution. Such methods can identify a shoreline by means of automatic, semi-automatic, or manual procedures. The aim of this work is to find and promote a new and valid beach topography-based algorithm, able to identify the shoreline. We apply the Structure from Motion (SfM) techniques to reconstruct a high-resolution Digital Elevation Model by means of a drone for image acquisition. The algorithm is based on the variation of the topographic beach profile caused by the transition from water to sand. The SfM technique is not efficient when applied to reflecting surfaces like sea water resulting in a very irregular and unnatural profile over the sea. Taking advantage of this fact, the algorithm searches for the point in the space where a beach profile changes from irregular to regular, causing a transition from water to land. The algorithm is promoted by the release of a QGIS v3.x plugin, which allows the easy application and extraction of other shorelines.
2
Xia, Geng, Caroline Draxl, Michael Optis, and Stephanie Redfern. "Detecting and characterizing simulated sea breezes over the US northeastern coast with implications for offshore wind energy." Wind Energy Science 7, no. 2 (April 5, 2022): 815–29. http://dx.doi.org/10.5194/wes-7-815-2022.
Full textAbstract:
Abstract. With the planned construction of vast offshore wind farms along the US East Coast, identifying and understanding key coastal processes, such as sea breezes, has become a critical need for the sustainability and development of US offshore wind energy. In this study, a new two-step identification method is proposed to detect and characterize three types of sea breezes (pure, corkscrew and backdoor) over the US northeastern coast from a year-long WRF (Weather Research and Forecasting) simulation. The results suggest that the proposed detection method can identify the three different types of sea breezes in the model simulation. Key sea breeze features, such as the calm zone associated with pure sea breezes and coastal jets associated with corkscrew sea breezes, are evident in the sea breeze composite imagery. In addition, the simulated sea breeze events indicate a seasonal transition from pure to corkscrew sea breeze between March and August as the land–sea thermal contrast increases. Furthermore, the location and extension of the sea breeze front are different for each type of sea breeze, suggesting that the coastal impact of sea breeze varies with sea breeze type. From the wind energy perspective, the power production associated with a 10 MW offshore wind turbine would be approximately 3 to 4 times larger during a corkscrew sea breeze event than the other two types of sea breezes. This highlights the importance of identifying the correct type of sea breeze in numerical weather/wind energy forecasting.
3
Dangendorf, Sönke, Marta Marcos, Guy Wöppelmann, Clinton P. Conrad, Thomas Frederikse, and Riccardo Riva. "Reassessment of 20th century global mean sea level rise." Proceedings of the National Academy of Sciences 114, no. 23 (May 22, 2017): 5946–51. http://dx.doi.org/10.1073/pnas.1616007114.
Full textAbstract:
The rate at which global mean sea level (GMSL) rose during the 20th century is uncertain, with little consensus between various reconstructions that indicate rates of rise ranging from 1.3 to 2 mm⋅y−1. Here we present a 20th-century GMSL reconstruction computed using an area-weighting technique for averaging tide gauge records that both incorporates up-to-date observations of vertical land motion (VLM) and corrections for local geoid changes resulting from ice melting and terrestrial freshwater storage and allows for the identification of possible differences compared with earlier attempts. Our reconstructed GMSL trend of 1.1 ± 0.3 mm⋅y−1 (1σ) before 1990 falls below previous estimates, whereas our estimate of 3.1 ± 1.4 mm⋅y−1 from 1993 to 2012 is consistent with independent estimates from satellite altimetry, leading to overall acceleration larger than previously suggested. This feature is geographically dominated by the Indian Ocean–Southern Pacific region, marking a transition from lower-than-average rates before 1990 toward unprecedented high rates in recent decades. We demonstrate that VLM corrections, area weighting, and our use of a common reference datum for tide gauges may explain the lower rates compared with earlier GMSL estimates in approximately equal proportion. The trends and multidecadal variability of our GMSL curve also compare well to the sum of individual contributions obtained from historical outputs of the Coupled Model Intercomparison Project Phase 5. This, in turn, increases our confidence in process-based projections presented in the Fifth Assessment Report of the Intergovernmental Panel on Climate Change.
4
Tri Martuti, Nana Kariada, Yustinus Ulung Anggraito, and Septiana Anggraini. "Vegetation Stratification in Semarang Coastal Area." Biosaintifika: Journal of Biology & Biology Education 11, no. 1 (April 1, 2019): 139–47. http://dx.doi.org/10.15294/biosaintifika.v11i1.18621.
Full textAbstract:
The coastal region is a dynamic area as a transition between the land and the sea. The ecological function of the coastal area is affected mainly by the structure and composition of vegetation factors. This study aims to analyze the vegetation stratification of terrestrial to marine ecosystems in the coastal area of Semarang City, Central Java Indonesia as an effort to manage a sustainable ecosystem. A striped path combined with nested plots were applied in this research. The plots were placed by systematic purposive sampling based on the homogeneity of vegetation found along with the topographic conditions of the research location. Analysis of qualitative data used by way of inventorying plants and identifying plants based on morphological characteristics that can be observed. Data analysis was performed based on the results of an inventory of the structure and composition of vegetation obtained including the index of diversity, evenness, and species richness. The results of plant identification found in the three locations recorded 51 plant species consisting of 29 families. The different types of vegetation in Taman Lele, Tapak, and Tirang Beach affect the diversity, richness, and evenness index of vegetation in all three locations. Therefore, it can be concluded that different environmental factors contribute to the vegetation stratification from the land to the sea. This is the first report on the Semarang coastal area vegetation stratification. The results can have a positive impact on the coastal area conservation strategy for sustainable management, as well as to be a media for environmental education purpose.
5
Hu, J., L. Lu, J. Xu, and J. Zhang. "A FAST SEGMENTATION ALGORITHM FOR C-V MODEL BASED ON EXPONENTIAL IMAGE SEQUENCE GENERATION." ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XLII-2/W7 (September 13, 2017): 761–64. http://dx.doi.org/10.5194/isprs-archives-xlii-2-w7-761-2017.
Full textAbstract:
For the island coastline segmentation, a fast segmentation algorithm for C-V model method based on exponential image sequence generation is proposed in this paper. The exponential multi-scale C-V model with level set inheritance and boundary inheritance is developed. The main research contributions are as follows: 1) the problems of the "holes" and "gaps" are solved when extraction coastline through the small scale shrinkage, low-pass filtering and area sorting of region. 2) the initial value of SDF (Signal Distance Function) and the level set are given by Otsu segmentation based on the difference of reflection SAR on land and sea, which are finely close to the coastline. 3) the computational complexity of continuous transition are successfully reduced between the different scales by the SDF and of level set inheritance. Experiment results show that the method accelerates the acquisition of initial level set formation, shortens the time of the extraction of coastline, at the same time, removes the non-coastline body part and improves the identification precision of the main body coastline, which automates the process of coastline segmentation.
6
Wu, Feng, Mei Li, Baowen Liao, Xin Shi, and Yong Xu. "DNA Barcoding Analysis and Phylogenetic Relation of Mangroves in Guangdong Province, China." Forests 10, no. 1 (January 12, 2019): 56. http://dx.doi.org/10.3390/f10010056.
Full textAbstract:
Mangroves are distributed in the transition zone between sea and land, mostly in tropical and subtropical areas. They provide important ecosystem services and are therefore economically valuable. DNA barcoding is a useful tool for species identification and phylogenetic reconstruction. To evaluate the effectiveness of DNA barcoding in identifying mangrove species, we sampled 135 individuals representing 23 species, 22 genera, and 17 families from Zhanjiang, Shenzhen, Huizhou, and Shantou in the Guangdong province, China. We tested the universality of four DNA barcodes, namely rbcL, matK, trnH-psbA, and the internal transcribed spacer of nuclear ribosomal DNA (ITS), and examined their efficacy for species identification and the phylogenetic reconstruction of mangroves. The success rates for PCR amplification of rbcL, matK, trnH-psbA, and ITS were 100%, 80.29% ± 8.48%, 99.38% ± 1.25%, and 97.18% ± 3.25%, respectively, and the rates of DNA sequencing were 100%, 75.04% ± 6.26%, 94.57% ± 5.06%, and 83.35% ± 4.05%, respectively. These results suggest that both rbcL and trnH–psbA are universal in mangrove species from the Guangdong province. The highest success rate for species identification was 84.48% ± 12.09% with trnH-psbA, followed by rbcL (82.16% ± 9.68%), ITS (66.48% ± 5.97%), and matK (65.09% ± 6.00%), which increased to 91.25% ± 9.78% with the addition of rbcL. Additionally, the identification rate of mangroves was not significantly different between rbcL + trnH-psbA and other random fragment combinations. In conclusion, rbcL and trnH-psbA were the most suitable DNA barcode fragments for species identification in mangrove plants. When the phylogenetic relationships were constructed with random fragment combinations, the optimal evolutionary tree with high supporting values (86.33% ± 4.16%) was established using the combination of matK + rbcL + trnH-psbA + ITS in mangroves. In total, the 476 newly acquired sequences in this study lay the foundation for a DNA barcode database of mangroves.
7
Cuccoli, Fabrizio, Luca Facheris, and Francesco Sermi. "Coordinate Registration Method based on Sea/Land Transitions Identification for Over-the-Horizon Sky-Wave Radar: Numerical Model and Basic Performance Requirements." IEEE Transactions on Aerospace and Electronic Systems 47, no. 4 (2011): 2974–85. http://dx.doi.org/10.1109/taes.2011.6034678.
Full text
8
Piacentini, Daniela, Francesco Troiani, Davide Torre, and Marco Menichetti. "Land-Surface Quantitative Analysis to Investigate the Spatial Distribution of Gravitational Landforms along Rocky Coasts." Remote Sensing 13, no. 24 (December 9, 2021): 5012. http://dx.doi.org/10.3390/rs13245012.
Full textAbstract:
The increasing availability of high-quality digital elevation models (DEMs) has been associated with a growing interest in developing quantitative analyses aimed at taking advantage of these detailed, updated, and promising digital datasets. Land-surface quantitative (LSQ) analysis is valuable for describing the land-surface topography and performing measures of the signature of specific geomorphic processes, taking into account site-specific geological contexts and morphoclimatic settings, proving to be particularly effective in transitional environments, such as rocky coasts. This paper presents the results of research aimed at investigating the spatial distribution of gravitational landforms along rocky coasts, by means of LSQ analysis based on a DEM with a ground resolution of 2 m, derived from airborne LiDAR (light detection and ranging) surveys. The study area is at Mt. San Bartolo (Northern Marche, Italy) and characterized by a sea cliff diffusely affected by gravitational phenomena of different sizes and types. Geomorphological and geological field data, interpretations of remotely sensed datasets derived from ad hoc unmanned aerial vehicle (UAV) flights, and DEM-derived hillshades were also adapted to support LSQ analysis. In detail, four morphometric variables (slope, roughness, terrain ruggedness index, and elevation standard deviation) were computed and the outputs evaluated based on visual–spatial inspections of derived raster datasets, descriptive statistics, and joint comparison. Results reveal the best performing variables and how combined interpretations can support the identification and mapping of zones characterized by varying spatial distribution of gravitational landforms of different types. The findings achieved along the Mt. San Bartolo rocky coast confirm that an approach based on land-surface quantitative analysis can act as a proxy to efficiently investigate gravitational slope processes in coastal areas, especially those that are difficult to reach with traditional field surveys.
9
Dachev, D., and S. Zlatanova. "Pollution sources identification in the “land-sea” system." Water Science and Technology 46, no. 8 (October 1, 2002): 53–58. http://dx.doi.org/10.2166/wst.2002.0144.
Full textAbstract:
It is our opinon that the new scientific thinking and education in the 21st century will increase the significance of the multidisciplinary nature knowledge. The nature of the marine sediments as well as the biochemical features of the littoral organisms appear to be in close relation to the geochemical impact of the coastal onshore. The biogeochemical analysis of the terrestrial and marine biocenosis is still fragmental, without balance between the casual and sequential relationships. Along the Bulgarian Black Sea coast the latter necessitates the geological pattern clarification of the areas south of Bourgas. Even a superficial overview of the geological features of the region highlights the impact of the geochemical anomalies related to Rosen and Zidarovo volcanic apparatuses and intrusions, other ore deposits south and south-west as well. However, the intensive anthropogenic impact on the geochemical haloes should be pointed out in the complex of ecological damage to the coast. Through complementary geoecological studies a significant updating of the knowledge is suggested. The geoecological mapping is needed to present the ratio of the lands saturated with geonoxes, and anthropogenically polluted ones. The new methodology recommended was applied to make the distinction of such lands in the regions of Pirdop and Kardjali. Another key element appears to be the ecologicalÐeconomic characteristics in the offshore-onshore balance. The marine resources will be studied in the alternative context: benefit-damage from the onshore polluters, and the biogeochemical characteristics of the littoral zone. The coastal areas environmental status should make a distinction between the environmentally undamaged, environmentally damaged by nature, anthropogenically damaged and complex damaged lands. Each ecological study or analysis presenting the ecological condition of the environment in a status quo (at a certain moment and at a certain location) is described in this work as a Status Geoecological System. For environmental management and protection of the Black Sea we refer to an indispensable Data File representing the Dynamic Geoecological System.
10
Durand, Pierre, Aime Druilhet, and Serge Briere. "A Sea-Land Transition Observed during the COAST Experiment." Journal of the Atmospheric Sciences 46, no. 1 (January 1989): 96–116. http://dx.doi.org/10.1175/1520-0469(1989)046<0096:asltod>2.0.co;2.
Full textDissertations / Theses on the topic "Sea/Land Transition identification"
1
Chaston, Katherine A. V. "Sediment nutrient bioavailability in a sub-tropical catchment dominated by agriculture : the transition from land to sea /." [St. Lucia, Qld.], 2001. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe17118.pdf.
Full text
2
Potard, Kevin. "Les émissions de composés organiques volatiles (COVs) des sols dans les paysages agricoles : identification des sources et incidences sur la qualité de l'air." Thesis, Rennes 1, 2017. http://www.theses.fr/2017REN1B058/document.
Full textAbstract:
Les composés Organiques Volatils (COVs) sont des gaz carbonés rares, émis en faible concentration depuis les surfaces continentale et marine vers l’atmosphère. Très réactifs, ces composés sont impliqués dans la chimie atmosphérique et sont au cœur de nombreuses problématiques environnementales actuelles telles que le changement climatique lié aux gaz à effet de serre, la qualité de l’air et les rétroactions sur le fonctionnement des écosystèmes. Les couverts végétaux terrestres étaient jusqu’alors identifiés comme les sources principales de COVs d’origine biogénique. Mais, de récentes études suggèrent que les sols pourraient constituer des sources majeures de COVs. Or dans les paysages anthropisés agricoles, les sols sont l’objet d’usages et de gestions divers et variés et sont susceptibles de modifier qualitativement et quantitativement les patrons d’émissions de COVs. Paradoxalement, les sols d’agrosystèmes ont fait l’objet de peu d’inventaires de leurs émissions de COVs. La rareté des connaissances sur la contribution des sols d’agrosystèmes dans les émissions de COVs a motivé ce travail de thèse dans lequel trois objectifs ont été poursuivis : i) inventorier les spectres et quantifier les flux de COVs émis par les sols dans les paysages agricoles, ii) déterminer le rôle des microorganismes du sol dans les émissions et iii) identifier les déterminants abiotiques régulant les émissions de COVs par les sols. Une première partie du travail a consisté à analyser les dynamiques temporelles d’émissions de COVs sur le terrain, dans deux sites observatoires représentatifs du paysage agricole Breton : le site EFELE (SOERE-PRO) comprenant des sols cultivés soumis à des pratiques de fertilisation contrastées, et la Zone Atelier Armorique (ZAAr) comprenant des prairies permanentes fertilisées et des prairies humides caractérisées par un faible degré d’anthropisation. La deuxième partie du travail a été menée en laboratoire pour expliciter et compléter les observations de terrain, deux séries d’expérimentations en laboratoire ont été réalisées permettant de manipuler, i) la source de carbone organique du sol via l’apport de différentes molécules modèles, ii) les communautés microbiennes par la transplantation de communautés microbiennes naturelles dans trois sols distincts. Cette étude aura permis de montrer, en laboratoire et sur le terrain, qu’un sol émet une quarantaine de masses dont seules quelques-unes (1 à 4) sont dominantes. Ces spectres de COVs sont par ailleurs spécifiques des usages des sols (culture vs prairie) et des pratiques de fertilisation. Nous montrons aussi : i) qu’il existe une temporalité des émissions de COVs par les sols allant de 22 à 167 μg de COVs par m−2 h−1, la période hivernale étant la moins émissive et que ii) s’ajoute que certaines pratiques de fertilisation, comme l’apport de lisier de porc, induisent un flux de méthanol pouvant atteindre jusqu’à 10 fois celui qui est observé par les sols amendés avec du digestat de lisier de porc. Concernant, le rôle des microorganismes du sol dans la production de COVs, nous démontrons que le spectre de COVs n’est pas représentatif de la diversité phylogénétique de la communauté du sol mais plutôt de l’activité métabolique des microorganismes actifs. S’agissant de l’exploration des déterminants abiotiques susceptibles de réguler les émissions, nos résultats suggèrent que l’ajout de molécules organiques au sol, induit un changement rapide dans le spectre de COVs émis par le sol. Cette modification est dépendante du degré de polymérisation de la molécule apportée. Pour conclure, l’approche intégrative et interdisciplinaire mise en œuvre dans ce travail de thèse a permis d’accroître les connaissances sur les émissions de COVs biogéniques par les sols. L’ensemble des recherches suggère que les émissions de COVs par les sols ne sont pas négligeables. Leur position dans les cycles biogéochimiques nécessite leur intégration dans les scenarii futurs des changements globauxVolatile Organic Compounds (VOCs) are trace carbonaceous gases emitted in low concentrations from the continental and marine surfaces to the atmosphere. Highly reactive, these compounds are involved in atmospheric chemistry and are at the heart of many current environmental issues such as climate change related to greenhouse gases, air quality and feedback on the functioning of ecosystems. Terrestrial plant cover was previously identified as the main source of VOCs of biogenic origin. But recent studies suggest that soils could be major sources of VOCs. However, in agricultural anthropogenic landscapes, soils are subject to various and varied uses and management and are likely to modify qualitatively and quantitatively the patterns of VOC emissions. Paradoxically, agrosystem soils have been the subject of few inventories of their VOC emissions. The scarcity of knowledge on the contribution of agrosystems soils in VOC emissions motivated this work of thesis in which three objectives were pursued : i) inventory the spectra and quantify the VOCs fluxes emitted by soils in agricultural landscapes (ii) to determine the role of soil microorganisms in emissions and (iii) to identify the abiotic determinants controlling VOC emissions by soils. A first part of the work has consisted in analyzing the temporal dynamics of VOCs emissions in the field, in two observatory sites representative of the Britain agricultural landscape : the EFELE site (SOERE-PRO) comprising cultivated soils subjected to contrasting fertilization practices, and the Zone Atelier Armorique (ZAAr) including fertilized permanent meadows and wet meadows characterized by a low degree of anthropization. The second step of the work was conducted in the laboratory to clarify and complete the field observations, two series of laboratory experiments were conducted to manipulate, i) the soil organic carbon source via the input of different model molecules (ii) microbial communities by transplanting natural microbial communities into three distinct soils. This study has generated technical advances and produced entirely new results concerning both the characterization of spectra and the quantification of biogenic VOC fluxes emitted by soils. Thus, we show, in the laboratory and in the field, that a soil emits about forty masses of which only a few (1 to 4) are dominant. These VOC spectra are also specific to land uses (crop vs meadow) and fertilization practices. We also show that : i) there is a temporality of VOC emissions by soils ranging from 22 to 167 μg of VOCs per m−2 h−1, the winter period is the least emissive and ii) adds that some fertilization practices, such as pig slurry, induce a flux of methanol up to 10 times that observed by soils amended with methanised pig slurry. Regarding the role of soil microorganisms in VOCs production, we demonstrate that the VOCs spectrum is not representative of the phylogenetic diversity of the soil community but rather of the metabolic activity of active microorganisms. As for the exploration of abiotic determinants that can regulate emissions, our results suggest that the addition of organic molecules to the soil induces a rapid change in the VOC spectrum emitted by the soil, ranging from a few hours to a few days after intake. This modification is dependent on the degree of polymerization of the molecule provided. All research suggests that VOC emissions by soils are not negligible. Their key position in terms of issues requires to be of greater interest and to take them into account in future scenarios of global changes (climate and land uses), especially with regard to emerging practices of soil management in connection with the ecological transition initiated in agriculture. Similarly, the consideration of VOCs emissions in the biogeochemical cycles of carbon and that of nitrogen to better understand the functioning of ecosystems is also discussed in this document
3
Habel, Chad Sean, and chad habel@gmail com. "Ancestral Narratives in History and Fiction: Transforming Identities." Flinders University. Humanities, 2006. http://catalogue.flinders.edu.au./local/adt/public/adt-SFU20071108.133216.
Full textAbstract:
This thesis is an exploration of ancestral narratives in the fiction of Thomas Keneally and Christopher Koch. Initially, ancestry in literature creates an historical relationship which articulates the link between the past and the present. In this sense ancestry functions as a type of cultural memory where various issues of inheritance can be negotiated. However, the real value of ancestral narratives lies in their power to aid in the construction of both personal and communal identities. They have the potential to transform these identities, to transgress natural boundaries and to reshape conventional identities in the light of historical experience.
For Keneally, ancestral narratives depict national forbears who narrate the nation into being. His earlier fictions present ancestors of the nation within a mythic and symbolic framework to outline Australian national identity. This identity is static, oppositional, and characterized by the delineation of boundaries which set nations apart from one another. However, Keneallys more recent work transforms this conventional construction of national identity. It depicts an Irish-Australian diasporic identity which is hyphenated and transgressive: it transcends the conventional notion of nations as separate entities pitted against one another. In this way Keneallys ancestral narratives enact the potential for transforming identity through ancestral narrative.
On the other hand, Kochs work is primarily concerned with the intergenerational trauma causes by losing or forgetting ones ancestral narrative. His novels are concerned with male gender identity and the fragmentation which characterizes a self-destructive idea of maleness. While Keneallys characters recover their lost ancestries in an effort to reshape their idea of what it is to be Australian, Kochs main protagonist lives in ignorance of his ancestors life. He is thus unable to take the opportunity to transform his masculinity due to the pervasive cultural amnesia surrounding his family history and its role in Tasmanias past.
While Keneally and Koch depict different outcomes in their fictional ancestral narratives they are both deeply concerned with the potential to transform national and gender identities through ancestry.
4
SERMI, FRANCESCO. "Digital processing of the echo received by an Over The Horizon (OTHR) Sky-Wave (SW) Radar System for Geo-Referencing of radar footprint through the identification of Sea/Land transition." Doctoral thesis, 2013. http://hdl.handle.net/2158/799653.
Full textAbstract:
Abstract:
Over-the-horizon radars (OTHRs) are HF-band systems that, via surface propagation (ground-wave or surface-wave) or ionospheric re
ection (sky-wave), cover an area that is located well beyond the horizon. Though based on an assessed technology, OTHRs are attracting today much interest, thanks to the relevant improvements in signal processing and data storage techniques. By exploiting the
propagation mechanisms of HF waves in the Terrestrial Atmosphere, the OTHR is able to overcome the horizon line, that represents a natural boundary for every ground-based microwave radar. In the case of sky-wave OTHR, the re
flection of the signals by the Ionosphere allows the system to achieve range distances up to about 3000 km. Nevertheless, the employment of the Ionosphere as part of the propagation-channel introduces an intrinsic uncertainty about the actual HF wave propagation path and, consequently, about the actual geographic position of the radar footprint. In fact, the non-homogeneous structure and time-dependent behavior of the Ionosphere make the a priori models for the propagation channel absolutely useless for a correct Geo-referencing of the received echo. Therefore, every HF OTHR-SW application must include a process to associated the received signals to unambiguous geographic coordinates. Such a process, referred to as coordinate registration (CR), generally relies on an ionospheric model, based on seasonal and daily ionospheric statistics within the radar operating area. Several current OTHR-SW systems perform a periodic update of the ionospheric model exploiting information gathered by ionosonde networks or directly collected from
the OTHR with a dedicated procedure. Both approaches exhibit several limitations, leading to a correct characterization of the ionosphere only when it is in particularly steady conditions.
The present research is focused on the study and development of a new different approach to the CR problem for OTHR-SW systems. This approach, referred to as Sea/Land Transition Identification (SLTI), takes advantage from the a priori knowledge of the Geo-morphological structure of the surveillance area in order to compensate for the uncertainties introduced by the Ionosphere. In fact, as suggested by the name of the method, the shape of the coastline profiles within the surveillance area are employed as position-references for the geo-referencing of the received radar echo. This task is possible through a basic time analysis of the echo, thanks to the marked difference in the values of the HF back-scattering coefficient for sea and land regions. The SLTI method is based on the maximization of the cross-correlation between the received radar echo and the surface mask signatures for the surveillance area. It can be employed in real time by the system, during its typical surveillance routine and besides the collected data can be exploited to estimate some Ionospheric parameters in order to periodically update and correct the employed statistical model.
After a general introduction about the OTHR sensors and a more detailed description of the sky-wave system who we refer to in the present work, the state of the art for the CR procedures actually employed by OTHR-SW is presented. Hence the SLTI method is outlined together with the numerical model of the whole OTHR-SW scenario. The application of the method, in this scenario simulated under simplifying operative hypothesis, is described with the help of some examples for both the CR procedure and the Ionospheric probing task. Within these examples of application of the SLTI method, the minimum requirements in terms of received signal-to-noise ratio (SNR) and differential sea/land backscattering coefficients necessary to achieve a given accuracy in the range estimate are pointed out. Finally the further developments of the SLTI method and some possible improvement of the simulated OTHR-SW's scenario are pointed out.
Books on the topic "Sea/Land Transition identification"
1
Vuorinen, Ilppo. Post-Glacial Baltic Sea Ecosystems. Oxford University Press, 2018. http://dx.doi.org/10.1093/acrefore/9780190228620.013.675.
Full textAbstract:
Post-glacial aquatic ecosystems in Eurasia and North America, such as the Baltic Sea, evolved in the freshwater, brackish, and marine environments that fringed the melting glaciers. Warming of the climate initiated sea level and land rise and subsequent changes in aquatic ecosystems. Seminal ideas on ancient developing ecosystems were based on findings in Swedish large lakes of species that had arrived there from adjacent glacial freshwater or marine environments and established populations which have survived up to the present day. An ecosystem of the first freshwater stage, the Baltic Ice Lake initially consisted of ice-associated biota. Subsequent aquatic environments, the Yoldia Sea, the Ancylus Lake, the Litorina Sea, and the Mya Sea, are all named after mollusc trace fossils. These often convey information on the geologic period in question and indicate some physical and chemical characteristics of their environment. The ecosystems of various Baltic Sea stages are regulated primarily by temperature and freshwater runoff (which affects directly and indirectly both salinity and nutrient concentrations). Key ecological environmental factors, such as temperature, salinity, and nutrient levels, not only change seasonally but are also subject to long-term changes (due to astronomical factors) and shorter disturbances, for example, a warm period that essentially formed the Yoldia Sea, and more recently the “Little Ice Age” (which terminated the Viking settlement in Iceland).There is no direct way to study the post-Holocene Baltic Sea stages, but findings in geological samples of ecological keystone species (which may form a physical environment for other species to dwell in and/or largely determine the function of an ecosystem) can indicate ancient large-scale ecosystem features and changes. Such changes have included, for example, development of an initially turbid glacial meltwater to clearer water with increasing primary production (enhanced also by warmer temperatures), eventually leading to self-shading and other consequences of anthropogenic eutrophication (nutrient-rich conditions). Furthermore, the development in the last century from oligotrophic (nutrient-poor) to eutrophic conditions also included shifts between the grazing chain (which include large predators, e.g., piscivorous fish, mammals, and birds at the top of the food chain) and the microbial loop (filtering top predators such as jellyfish). Another large-scale change has been a succession from low (freshwater glacier lake) biodiversity to increased (brackish and marine) biodiversity. The present-day Baltic Sea ecosystem is a direct descendant of the more marine Litorina Sea, which marks the beginning of the transition from a primeval ecosystem to one regulated by humans. The recent Baltic Sea is characterized by high concentrations of pollutants and nutrients, a shift from perennial to annual macrophytes (and more rapid nutrient cycling), and an increasing rate of invasion by non-native species. Thus, an increasing pace of anthropogenic ecological change has been a prominent trend in the Baltic Sea ecosystem since the Ancylus Lake.Future development is in the first place dependent on regional factors, such as salinity, which is regulated by sea and land level changes and the climate, and runoff, which controls both salinity and the leaching of nutrients to the sea. However, uncertainties abound, for example the future development of the Gulf Stream and its associated westerly winds, which support the sub-boreal ecosystems, both terrestrial and aquatic, in the Baltic Sea area. Thus, extensive sophisticated, cross-disciplinary modeling is needed to foresee whether the Baltic Sea will develop toward a freshwater or marine ecosystem, set in a sub-boreal, boreal, or arctic climate.
2
Fikfak, Alenka, Saja Kosanović, Miha Konjar, and Enrico Anguillari, eds. SUSTAINABILITY AND RESILIENCE: socio-spatial perspective. TU Delft Bouwkunde, 2018. http://dx.doi.org/10.47982/bookrxiv.23.
Full textAbstract:
Sustainability and resilience have become indispensable parts of the contemporary debate over the built environment. Although recognised as imperatives, the complexity and the variety of interpretations of sustainability and resilience have raised the necessity to again rethink their notion in the context of the built environment and to reframe the state-of-the-art body of knowledge. The book Sustainability and Resilience: Socio-Spatial Perspective so begins with the exploration of the broadest conceptual frame-of-reference of issues related to sustainability, and the re-establishment of the connection between the built environment and the conditions that are vital to its functioning, primarily in relation to energy, land use, climate, and economy. Subsequent discussion on resilience as a term, approach, and philosophy aims to conceptualise an interpretation of key resilience concepts, explain relationships and links among them, and propose the classification of resilience as applicable to the context of urban studies. By studying the processes of transition of the built environment, the book then reveals a coherent formula of ‘thinking sustainability + resilience’ aimed at improving the ability to respond to disruptions and hazards while enhancing human and environmental welfare. The necessity to integrate the two approaches is further accented as a result of a deliberative discourse on the notions of ‘social sustainability’, ‘sustainable community’, and ‘socio-cultural resilience’. The potential of measuring sustainable development and urban sustainability on the basis of defined social, human, and, additionally, natural and economic values is presented though an overview of different wellknown indicators and the identification of a currently relevant tangible framework of sustainable development. Correspondingly, the role of policies and governance is demonstrated on the case of climate-proof cities. In this way, the consideration of approaches to sustainability and resilience of the urban environment is rounded, and the focus of the book is shifted towards an urban/rural dichotomy and the sustainability prospects of identified forms-in-between, and, subsequently, towards the exploration of values, challenges, and the socio-cultural role in achieving sustainability for rural areas. In the final chapters, the book offers several peculiarised socio-spatial perspectives, from defining the path towards more resilient communities and sustainable spaces based on a shared wellbeing, to proposing the approach to define community resilience as an intentional action that aims to respond to, and influence, the course of social and economic change, to deliberating the notion of a ’healthy place’ and questioning its optimal scale in the built environment. The study of sustainability and resilience in this book is concluded by drawing a parallel between environmental, economic, and social determinants of the built environment and the determinants that are relevant to human health and well-being.
3
Lézine, Anne-Marie. Vegetation at the Time of the African Humid Period. Oxford University Press, 2017. http://dx.doi.org/10.1093/acrefore/9780190228620.013.530.
Full textAbstract:
An orbitally induced increase in summer insolation during the last glacial-interglacial transition enhanced the thermal contrast between land and sea, with land masses heating up compared to the adjacent ocean surface. In North Africa, warmer land surfaces created a low-pressure zone, driving the northward penetration of monsoonal rains originating from the Atlantic Ocean. As a consequence, regions today among the driest of the world were covered by permanent and deep freshwater lakes, some of them being exceptionally large, such as the “Mega” Lake Chad, which covered some 400 000 square kilometers. A dense network of rivers developed.What were the consequences of this climate change on plant distribution and biodiversity? Pollen grains that accumulated over time in lake sediments are useful tools to reconstruct past vegetation assemblages since they are extremely resistant to decay and are produced in great quantities. In addition, their morphological character allows the determination of most plant families and genera.In response to the postglacial humidity increase, tropical taxa that survived as strongly reduced populations during the last glacial period spread widely, shifting latitudes or elevations, expanding population size, or both. In the Saharan desert, pollen of tropical trees (e.g., Celtis) were found in sites located at up to 25°N in southern Libya. In the Equatorial mountains, trees (e.g., Olea and Podocarpus) migrated to higher elevations to form the present-day Afro-montane forests. Patterns of migration were individualistic, with the entire range of some taxa displaced to higher latitudes or shifted from one elevation belt to another. New combinations of climate/environmental conditions allowed the cooccurrences of taxa growing today in separate regions. Such migrational processes and species-overlapping ranges led to a tremendous increase in biodiversity, particularly in the Saharan desert, where more humid-adapted taxa expanded along water courses, lakes, and wetlands, whereas xerophytic populations persisted in drier areas.At the end of the Holocene era, some 2,500 to 4,500 years ago, the majority of sites in tropical Africa recorded a shift to drier conditions, with many lakes and wetlands drying out. The vegetation response to this shift was the overall disruption of the forests and the wide expansion of open landscapes (wooded grasslands, grasslands, and steppes). This environmental crisis created favorable conditions for further plant exploitation and cereal cultivation in the Congo Basin.
4
Cook, Kerry H. Climate Change Scenarios and African Climate Change. Oxford University Press, 2018. http://dx.doi.org/10.1093/acrefore/9780190228620.013.545.
Full textAbstract:
Accurate projections of climate change under increasing atmospheric greenhouse gas levels are needed to evaluate the environmental cost of anthropogenic emissions, and to guide mitigation efforts. These projections are nowhere more important than Africa, with its high dependence on rain-fed agriculture and, in many regions, limited resources for adaptation. Climate models provide our best method for climate prediction but there are uncertainties in projections, especially on regional space scale. In Africa, limitations of observational networks add to this uncertainty since a crucial step in improving model projections is comparisons with observations. Exceeding uncertainties associated with climate model simulation are uncertainties due to projections of future emissions of CO2 and other greenhouse gases. Humanity’s choices in emissions pathways will have profound effects on climate, especially after the mid-century.The African Sahel is a transition zone characterized by strong meridional precipitation and temperature gradients. Over West Africa, the Sahel marks the northernmost extent of the West African monsoon system. The region’s climate is known to be sensitive to sea surface temperatures, both regional and global, as well as to land surface conditions. Increasing atmospheric greenhouse gases are already causing amplified warming over the Sahara Desert and, consequently, increased rainfall in parts of the Sahel. Climate model projections indicate that much of this increased rainfall will be delivered in the form of more intense storm systems.The complicated and highly regional precipitation regimes of East Africa present a challenge for climate modeling. Within roughly 5º of latitude of the equator, rainfall is delivered in two seasons—the long rains in the spring, and the short rains in the fall. Regional climate model projections suggest that the long rains will weaken under greenhouse gas forcing, and the short rains season will extend farther into the winter months. Observations indicate that the long rains are already weakening.Changes in seasonal rainfall over parts of subtropical southern Africa are observed, with repercussions and challenges for agriculture and water availability. Some elements of these observed changes are captured in model simulations of greenhouse gas-induced climate change, especially an early demise of the rainy season. The projected changes are quite regional, however, and more high-resolution study is needed. In addition, there has been very limited study of climate change in the Congo Basin and across northern Africa. Continued efforts to understand and predict climate using higher-resolution simulation must be sustained to better understand observed and projected changes in the physical processes that support African precipitation systems as well as the teleconnections that communicate remote forcings into the continent.
Book chapters on the topic "Sea/Land Transition identification"
1
Seibert, Stephan Ludger, Julius Degenhardt, Janis Ahrens, Anja Reckhardt, Kai Schwalfenberg, and Hannelore Waska. "Investigating the Land-Sea Transition Zone." In YOUMARES 9 - The Oceans: Our Research, Our Future, 225–42. Cham: Springer International Publishing, 2019. http://dx.doi.org/10.1007/978-3-030-20389-4_12.
Full text
2
Stal, Lucas J. "Coastal Sediments: Transition from Land to Sea." In The Marine Microbiome, 283–304. Cham: Springer International Publishing, 2016. http://dx.doi.org/10.1007/978-3-319-33000-6_10.
Full text
3
de Vries, Jan. "The transition to capitalism in a land without feudalism." In Comparative Rural History of the North Sea Area, 67–84. Turnhout: Brepols Publishers, 2001. http://dx.doi.org/10.1484/m.corn-eb.3.285.
Full text
4
Schlanger, Seymour O., and Robert G. Douglas. "The Pelagic Ooze-Chalk-Limestone Transition and its Implications for Marine Stratigraphy." In Pelagic Sediments: On Land and under the Sea, 117–48. Oxford, UK: Blackwell Publishing Ltd., 2009. http://dx.doi.org/10.1002/9781444304855.ch6.
Full text
5
Beckett, John V., and Michael E. Turner. "14. Freehold from copyhold and leasehold. Tenurial transition in England between the 16th and 19th centuries." In Landholding and Land Transfer in the North Sea Area (Late Middle Ages - 19th Century), 282–92. Turnhout: Brepols Publishers, 2004. http://dx.doi.org/10.1484/m.corn-eb.4.00150.
Full text
6
Mulyani, Laily Fitriani, Nanda Diniarti, and Bagus Dwi Hari Setyono. "Mapping Identification of Sea Water Characteristics for Cultivation Land for Giant Clams (Family: Tridacnidae) in Sekotong West Lombok." In Proceedings of the First Mandalika International Multi-Conference on Science and Engineering 2022, MIMSE 2022 (Informatics and Computer Science), 14–21. Dordrecht: Atlantis Press International BV, 2022. http://dx.doi.org/10.2991/978-94-6463-084-8_3.
Full text
7
Newton, Peter W., Peter W. G. Newman, Stephen Glackin, and Giles Thomson. "Integrating Transition Processes for Regenerating the Greyfields." In Greening the Greyfields, 171–87. Singapore: Springer Singapore, 2021. http://dx.doi.org/10.1007/978-981-16-6238-6_8.
Full textAbstract:
AbstractThis book has introduced two new (linked) models for greyfield precinct regeneration—place-activated and transit-activated GPR—with a new set of processes to enable them. The need for new design, planning, and engagement tools that must be integrated into all urban development is also seen as key to unlocking greyfield regeneration. Designs for such precincts have proliferated, but planning systems are still hindering their implementation, especially those systems related to land-assembly issues in the established, occupied middle greyfield suburbs. Planning must change, and a potential way ahead involves the planning processes demonstrated in this book. A first step involves district greenlining, which enables identification of strategic planning challenges and priorities for action at a district scale along a transit corridor (transit-activated GPR) or in precinct-scale areas in typical middle suburbs with high redevelopment potential (place-activated GPR). Their key attributes are gleaned from the previous chapters and summarised in this chapter. A final plea is made here for partnerships to be created from the engagement of all stakeholders: government, community and civil society, innovators, and developers. Greyfield Precinct Redevelopment Authorities established within state governments as part of a federal Better Cities 2.0 program could guide this transition.
8
"4. Natural Knowledge and a Bay in Transition." In Between Land and Sea, 130–60. Harvard University Press, 2014. http://dx.doi.org/10.4159/harvard.9780674736078.c6.
Full text
9
Morgan, Philip D., J. R. McNeill, Matthew Mulcahy, and Stuart B. Schwartz. "Conclusion: Caribbean Environmental History since 1850." In Sea and Land, 253—C4.T2. Oxford University PressNew York, 2022. http://dx.doi.org/10.1093/oso/9780197555446.003.0005.
Full textAbstract:
Abstract The concluding chapter sketches the continuing evolution of Caribbean landscapes and seascapes, the regimes of disease and health, and the role of natural disasters in the period after c.1850. It again centers Alexander von Humboldt, who, before his death in 1859, witnessed some of the new forces transforming the Caribbean environment, including the burgeoning power of the United States, the fracturing of the colonial system, the decline of slavery, the rise of peasant smallholdings, new technologies as in railroads and steamships, and rapidly growing urban populations. The region’s health history since 1850, and especially since 1970, has seen overall improvement and a reduction in the toll of infectious disease, due in part to an unusually rapid epidemiological transition from an old regime in which infectious disease and child malnutrition exerted the strongest influences upon mortality to a new one in which “diseases of affluence” end the vast majority of lives. Still, epidemics continued to batter the modern Caribbean, and healthcare remained unequally distributed. Dramatic and traumatic disasters likewise continued to beset the region, their impact shaped by ever shifting social, political, economic, and cultural forces at work—particularly in the modern era, increased urbanization and tourism. In sum, the environmental history of the Caribbean since 1850 has remained a function of the region’s place within the global economy and of its geographical and deep historical legacies. Although many key forces gradually diminished or disappeared, including slavery, the long legacies of the past still exert their grip across the Caribbean region.
10
Kudrass, Herman R., and Dennis A. Ardus. "Geological Techniques." In Continental Shelf Limits. Oxford University Press, 2000. http://dx.doi.org/10.1093/oso/9780195117820.003.0019.
Full textAbstract:
In the previous chapters, the use of geophysical data for delineating the continental shelf has been discussed in some detail. But the determination of the case for any extension of the legal continental shelf beyond 200 nautical miles (M) from the territorial sea baseline may in some circumstances require a geological survey to confirm that a topographic or geophysical feature comprising what appears to be a natural prolongation of land territory is of continental or oceanic origin. A geological survey may also be necessary to determine the occurrence, thickness, and extent of sediments beyond the foot of the slope. Continental margins represent regions of transition from the landmass to the ocean basin and may be present-day areas of sediment erosion or deposition. Sediment supply to the continental shelf and slope, or the extent of erosion on the continental shelf and upper slope, is influenced by tectonic activity, sea-level fluctuations, climate change, variation in the wave or current regime, and various other processes. Bottom currents or gravity transport (turbidity) processes combine to varying degrees with pelagic sedimentation (the accumulation of the remains of marine organisms) to extend the supply of sediment well beyond the shelf and slope to the continental rise, ocean trench, or abyssal plain (Evans et al., 1998). In order to understand the geology of such areas, it is necessary to determine the structural setting, the tectonic and sedimentary evolution, the chrono-and lithostratigraphy, and the volcanic history. Understanding the ocean floor is a prerequisite for the determination of the extent of the continental shelf under UNCLOS. It is also highly relevant to the identification and delineation of mineral and energy resources, for determining the waste disposal potential of parts of the seafloor, and for undertaking an assessment of the risk of slope failure. None of these are directly relevant to establishing the new limits of the continental shelf, but they are highly relevant to its long-term exploitation. In order to achieve the necessary level of knowledge, the seafloor morphology and seabed character derived from bathymetric and sonar surveys (described in chapters 9 and 10) and the three-dimensional geology determined by geophysical surveys using seismic profiling, magnetometer, and gravity meter (discussed in chapters 12 and 13) need to be calibrated or "ground truthed" by sampling and coring (figure 14.1; Stoker et al., 1994).
Conference papers on the topic "Sea/Land Transition identification"
1
McAuliffe, B. R., and M. I. Yaras. "Transition Mechanisms in Separation Bubbles Under Low and Elevated Freestream Turbulence." In ASME Turbo Expo 2007: Power for Land, Sea, and Air. ASMEDC, 2007. http://dx.doi.org/10.1115/gt2007-27605.
Full textAbstract:
Through numerical simulations, this paper examines the nature of instability mechanisms leading to transition in separation bubbles. The results of two direct numerical simulations are presented in which separation of a laminar boundary layer occurs over a flat surface in the presence of an adverse pressure gradient. The primary difference in the flow conditions between the two simulations is the level of freestream turbulence with intensities of 0.1% and 1.45% at separation. In the first part of the paper, transition under a low-disturbance environment is examined, and the development of the Kelvin-Helmholtz instability in the separated shear layer is compared to the well-established instability characteristics of free shear layers. The study examines the role of the velocity-profile shape on the instability characteristics and the nature of the large-scale vortical structures shed downstream of the bubble. The second part of the paper examines transition in a high-disturbance environment, where the above-mentioned mechanism is bypassed as a result of elevated freestream turbulence. Filtering of the freestream turbulence into the laminar boundary layer results in streamwise streaks which provide conditions under which turbulent spots are produced in the separated shear layer, grow, and then merge to form a turbulent boundary layer. The results allow identification of the structure of the instability mechanism and the characteristic structure of the resultant turbulent spots. Recovery of the reattached turbulent boundary layer is then examined for both cases. The large-scale flow structures associated with transition are noted to remain coherent far downstream of reattachment, delaying recovery of the turbulent boundary layer to an equilibrium state.
2
Van Treuren, Kenneth W., Terrence Simon, Marc von Koller, Aaron R. Byerley, James W. Baughn, and Richard Rivir. "Measurements in a Turbine Cascade Flow Under Ultra Low Reynolds Number Conditions." In ASME Turbo Expo 2001: Power for Land, Sea, and Air. American Society of Mechanical Engineers, 2001. http://dx.doi.org/10.1115/2001-gt-0164.
Full textAbstract:
With the new generation of gas turbine engines, low Reynolds number flows have become increasingly important. Designers must properly account for transition from laminar to turbulent flow and separation of the flow from the suction surface, which is strongly dependent upon transition. Of interest to industry are Reynolds numbers based upon suction surface length and flow exit velocity below 150,000 and as low as 25,000. In this paper, the extreme low end of this Reynolds number range is documented by way of pressure distributions, loss coefficients and identification of separation zones. Reynolds numbers of 25,000 and 50,000 and with 1% and 8–9% turbulence intensity of the approach flow (Free Stream Turbulence Intensity, FSTI) were investigated. At 25,000 Reynolds number and low FSTI, the suction surface displayed a strong and steady separation region. Raising the turbulence intensity resulted in a very unsteady separation region of nearly the same size on the suction surface. Vortex generators were added to the suction surface, but they appeared to do very little at this Reynolds number. At the higher Reynolds number of 50,000, the low-FSTI case was strongly separated on the downstream portion of the suction surface. The separation zone was eliminated when the turbulence level was increased to 8–9%. Vortex generators were added to the suction surface of the low-FSTI case. In this instance, the vortices were able to provide the mixing needed to reestablish flow attachment. This paper shows that massive separation at very low Reynolds numbers (25,000) is persistent, in spite of elevated FSTI and added vortices. However, at a higher Reynolds number, there is opportunity for flow reattachment either with elevated freestream turbulence or with added vortices. This may be the first documentation of flow behavior at such low Reynolds numbers. Though undesirable to operate under these conditions, it is important to know what to expect and how performance may be improved if such conditions are unavoidable.
3
Corral, Roque, and Fernando Gisbert. "Prediction of Separation-Induced Transition Using a Correlation-Based Transition Model." In ASME Turbo Expo 2010: Power for Land, Sea, and Air. ASMEDC, 2010. http://dx.doi.org/10.1115/gt2010-23239.
Full textAbstract:
A correlation-based transition model has been introduced in a RANS solver to improve the prediction of the transition from laminar to turbulent flow regime in low-pressure turbine blades. The model has been validated by comparing the numerical results against experimental data. The transition model correctly predicts the transition process due to the separation of the laminar boundary layer in a wide range of situations, ranging from steady two-dimensional simulations to unsteady multirow three-dimensional simulations with cavities, improving in all cases the sensitivity of the RANS solver to variations in the Reynolds number.
4
Dris, Antonis, and Mark W. Johnson. "Transition on Concave Surfaces." In ASME Turbo Expo 2004: Power for Land, Sea, and Air. ASMEDC, 2004. http://dx.doi.org/10.1115/gt2004-53352.
Full textAbstract:
Boundary layer measurements have been made on the concave surfaces of two constant curvature blades using hot wire anemometry. All the current experiments were performed with negligible streamwise pressure gradient. Grids were used to produce a range of freestream turbulence levels between 1% and 4%. The freestream velocity increases with distance from a concave wall according to the free vortex condition making the determination of the boundary layer edge difficult. A flat plate equivalent boundary layer procedure was adopted therefore to overcome this problem. The Taylor-Goertler (T-G) vortices resulting from the concave curvature were found to make the laminar and turbulent boundary layer profiles fuller and to increase the skin friction coefficent by up to 40% compared with flat plate values. This leads to a more rapid growth in boundary layer thickness. The evolution in the intermittency through transition is very similar to that for a flat plate, however the shape factors are depressed slightly throughout the flow due to the fuller velocity profiles. For all the current experiments, curvature promoted transition. This was very marked at low freestream turbulence level but remained significant even at the highest levels. It appears that the velocity fluctuations associated with the T-G vortices enhance the freestream turbulence resulting in a higher effective turbulence level. A new empirical correlation for start of transition based on this premise is presented. The ratio of end to start of transition momentum thickness Reynolds numbers was found to be approximately constant.
5
Roberts, S. K., and M. I. Yaras. "Modeling of Boundary-Layer Transition." In ASME Turbo Expo 2004: Power for Land, Sea, and Air. ASMEDC, 2004. http://dx.doi.org/10.1115/gt2004-53664.
Full textAbstract:
This paper presents a mathematical model for predicting the rate of turbulent spot production. In this model, attached- and separated-flow transition are treated in a unified manner, and the boundary layer shape factor is identified as the parameter with which the spot production rate correlates. The model is supplemented by several correlations to allow for its practical use in the prediction of the length of the transition zone. Secondly, the paper presents a model for the prediction of the location of transition inception in separation-bubbles. The model improves on the accuracy of existing alternatives, and is the first to account for the effects of surface roughness.
6
Johnson, Mark W. "Predicting Transition on Concave Surfaces." In ASME Turbo Expo 2006: Power for Land, Sea, and Air. ASMEDC, 2006. http://dx.doi.org/10.1115/gt2006-90455.
Full textAbstract:
Boundary layers on concave surfaces differ from those on flat plates due to the presence of Taylor Goertler (T-G) vortices. These vortices cause momentum transfer normal to the blade’s surface and hence result in a more rapid development of the laminar boundary layer and a fuller profile than is typical of a flat plate. Transition of boundary layers on concave surfaces also occurs at a lower Rex than on a flat plate. Concave surface transition correlations have been formulated previously from experimental data, but they are not comprehensive and are based on relatively sparse data. The purpose of the current work was to attempt to model the physics of both the laminar boundary layer development and transition process in order to produce a transition model suitable for concave surface boundary layers. The development of the laminar boundary layer on a concave surface was modeled by considering the profiles at the upwash and downwash locations separately. The profiles of the boundary layers at these two locations were then combined to successfully approximate the spanwise averaged profile. The ratio of the boundary layer thicknesses at the two locations was found to be as great as 50 and this leads to laminar boundary layer shape factors as low as 1.3 and skin friction coefficients up to 12 times the value for a flat plate laminar boundary layer. Boundary layers therefore grow much more rapidly on concave surfaces than on flat plates. The transition model assumed that transition commenced in the upwash location boundary layer at the same transition inception Reθ observed on a flat plate. Transition at the downwash location then results from the growth of turbulent spots from the upwash location rather than through the initiation of spots. The model showed that initially curvature promotes transition because of the thickened upwash boundary layer, but for strong curvature the T-G vortices effectively stabilise the boundary layer and transition then occurs at a higher Reθ than on a flat plate. Results from the transition model were in broad agreement with experimental observations. The current work therefore provides a basis for the modeling of transition on concave surfaces.
7
Kelterer, M. E., R. Pecnik, and W. Sanz. "Computation of Laminar-Turbulent Transition in Turbumachinery Using the Correlation Based γ-Reθ Transition Model." In ASME Turbo Expo 2010: Power for Land, Sea, and Air. ASMEDC, 2010. http://dx.doi.org/10.1115/gt2010-22207.
Full textAbstract:
The accurate numerical simulation of the flow through turbomachinery depends on the correct prediction of boundary-layer transition phenomena. Especially heat transfer and skin friction investigations demand a reliable simulation of the transition process. Many models have been developed to simulate the transition process, ranging from simple algebraic models to very sophisticated transport models. But nearly all models suffer from the need to determine boundary layer parameters and from their difficult application in three-dimensional flows. Therefore, in this work the correlation based γ-Reθ transition model developed by Menter and Langtry is implemented into the in-house Reynolds-averaged Navier-Stokes solver. This model avoids the calculation of non-local parameters and is thus very suitable for three-dimensional general flow situations. Two additional transport equations, one for the intermittency and one for the momentum thickness Reynolds number, which is a criterion for the transition onset, are added to the well known SST turbulence model by Menter. Instead of the proprietary model correlations by Menter et al. the authors used correlations by other research groups within the in-house code and tested these correlations for simple flat-plate test cases. The non-satisfying results indicate a strong code dependency of the model. Therefore also in-house correlations are presented and validated. A comprehensive study of the model performance on the well known ERCOFTAC flat plate test cases is performed. After this validation the model is applied to the steady flow in a T106A and a T106 turbine cascade.
8
Johnson, Mark W. "Predicting Transition Without Empiricism or DNS." In ASME Turbo Expo 2002: Power for Land, Sea, and Air. ASMEDC, 2002. http://dx.doi.org/10.1115/gt2002-30238.
Full textAbstract:
A numerical procedure for predicting the receptivity of laminar boundary layers to freestream turbulence consisting of vortex arrays with arbitrary orientation has been developed. Results show that the boundary layer is most receptivity to those vortices which have their axes approximately in the streamwise direction and vortex wavelengths of approximately 1.2 δ. The computed near wall gains for isotropic turbulence are similar in magnitude to previously published experimental values used to predict transition. The new procedure is therefore capable of predicting the development of the fluctuations in the laminar boundary layer from values of the freestream turbulence intensity and length scale and hence determining the start of transition without resorting to any empirical correlation.
9
Rendek, Pete, Link Jaw, and Gary Smith. "Successful Trending and Diagnostics Technology Transition." In ASME Turbo Expo 2007: Power for Land, Sea, and Air. ASMEDC, 2007. http://dx.doi.org/10.1115/gt2007-28026.
Full textAbstract:
Starting in 1998, the U.S. Air Force funded a Small Business Innovative Research (SBIR) contract to develop enhanced capabilities for trending, diagnostics, and health management for engines. The resulting technology platform, called ICEMS (Intelligent Condition-based Equipment Management System), includes an open-system architecture and a suite of tools to perform a full range of functions for engine health management, although the ICEMS technology platform is applicable to all types of equipment or systems [1]. The ICEMS technology is one of very few that have crossed the transition chasm in that it is being commercialized into the next generation of Air Force trending tool, the Diagnostic Analysis and Trending Tool (DATT), and into a commercial trending and analysis tool called I-Trend. This paper describes the tools and discusses some of the key factors in the successful commercialization of the SBIR technology.
10
Wallin, Fredrik, and Lars-Erik Eriksson. "Response Surface-Based Transition Duct Shape Optimization." In ASME Turbo Expo 2006: Power for Land, Sea, and Air. ASMEDC, 2006. http://dx.doi.org/10.1115/gt2006-90978.
Full textAbstract:
Demands on improved efficiency and reduced noise levels cause a strive toward very high by-pass ratio (BPR) turbo-fan-engines resulting in large fans and small high-pressure-ratio cores. The trend of increasing the radial offset between low- and high-pressure systems has made the design of intermediate transition ducts an area of growing importance. Shape optimization techniques for turbo-machinery applications have become a powerful aero-design tool and thanks to the rapid development of computer technology, computational fluid dynamics (CFD) may be used for optimization purposes. Surrogate model-based optimization has in recent years become a good alternative to the gradient-based search algorithms. One well-known surrogate model-based approach is response surface methodology (RSM), which has been used in the present work. RSM used together with design of experiments (DOE) can be a very efficient and robust method for CFD-based optimization. Optimization of two different transition ducts has been performed and evaluated; one 2D axi-symmetric turbine duct and one 3D compressor duct. The optimization objective was to minimize the total pressure loss. For the turbine duct both a high-Re and a low-Re turbulence closure were evaluated. The influence of design space size on the turbine duct optimization was investigated and for the 3D compressor duct the effects of adding an outflow constraint were examined. It has been found that end-wall optimization has the potential to reduce duct losses significantly. An early rapid diffusion and a stream-wise curvature shift toward the outlet seem to be important mechanisms for reducing transition duct losses.
Reports on the topic "Sea/Land Transition identification"
1
Beck, Aaron. RiverOceanPlastic: Land-ocean transfer of plastic debris in the North Atlantic, Cruise No. AL534/2, 05 March – 26 March 2020, Malaga (Spain) – Kiel (Germany). GEOMAR Helmholtz Centre for Ocean Research Kiel, 2020. http://dx.doi.org/10.3289/cr_al534-2.
Full textAbstract:
Cruise AL534/2 is part of a multi-disciplinary research initiative as part of the JPI Oceans project HOTMIC and sought to investigate the origin, transport and fate of plastic debris from estuaries to the oceanic garbage patches. The main focus of the cruise was on the horizontal transfer of plastic debris from major European rivers into shelf regions and on the processes that mediate this transport. Stations were originally chosen to target the outflows of major European rivers along the western Europe coast between Malaga (Spain) and Kiel (Germany), although some modifications were made in response to inclement weather. In total, 16 stations were sampled along the cruise track. The sampling scheme was similar for most stations, and included: 1) a CTD cast to collect water column salinity and temperature profiles, and discrete samples between surface and seafloor, 2) sediment sampling with Van Veen grab and mini-multi corer (mini-MUC), 3) suspended particle and plankton sampling using a towed Bongo net and vertical WP3 net, and 4) surface neusten sampling using a catamaran trawl. At a subset of stations with deep water, suspended particles were collected using in situ pumps deployed on a cable. During transit between stations, surface water samples were collected from the ship’s underway seawater supply, and during calm weather, floating litter was counted by visual survey teams. The samples and data collected on cruise AL534/2 will be used to determine the: (1) abundance of plastic debris in surface waters, as well as the composition of polymer types, originating in major European estuaries and transported through coastal waters, (2) abundance and composition of microplastics (MP) in the water column at different depths from the sea surface to the seafloor including the sediment, (3) abundance and composition of plastic debris in pelagic and benthic organisms (invertebrates), (4) abundance and identity of biofoulers (bacteria, protozoans and metazoans) on the surface of plastic debris from different water depths, (5) identification of chemical compounds (“additives”) in the plastic debris and in water samples.