161,281 research outputs found
Phillip Lai monograph (2022)
No full textThis first monograph on Phillip Lai (b.1969, Kuala Lumpur, Malaysia) charts the artist’s sculptural development over the course of the last two decades. From a basement soy-sauce factory to the Hepworth Prize for Sculpture, the publication surveys several of the artist’s exhibitions across London, Wakefield, Turin, Berlin and Hong Kong. The nine chapters explore an evolving oeuvre that finds form in materials like aluminium, pewter, concrete, resin, rice, cooking pots, textiles and film. It is through these technologies that Lai broaches the material limits of the everyday world, often working with casting processes that see the abstraction and changing stability of materials as they transition from fluid to solid. What comes into focus is a fascination with how objects can relieve or modulate primal human urges to food and water and how, by extension, a material world might be re-envisioned around concerns of depletion and survival. This publication includes an essay by critic and writer Jan Verwoert, with bilingual text in English and Chinese throughout
Optimal Exploitation of the Sentinel-2 Spectral Capabilities for Crop Leaf Area Index Mapping
No full textThe continuously increasing demand of accurate quantitative high quality information on land surface properties will be faced by a new generation of environmental Earth observation (EO) missions. One current example, associated with a high potential to contribute to those demands, is the multi-spectral ESA Sentinel-2 (S2) system. The present study focuses on the evaluation of spectral information content needed for crop leaf area index (LAI) mapping in view of the future sensors. Data from a field campaign were used to determine the optimal spectral sampling from available S2 bands applying inversion of a radiative transfer model (PROSAIL) with look-up table (LUT) and artificial neural network (ANN) approaches. Overall LAI estimation performance of the proposed LUT approach (LUTN₅₀) was comparable in terms of retrieval performances with a tested and approved ANN method. Employing seven- and eight-band combinations, the LUTN₅₀ approach obtained LAI RMSE of 0.53 and normalized LAI RMSE of 0.12, which was comparable to the results of the ANN. However, the LUTN50 method showed a higher robustness and insensitivity to different band settings. Most frequently selected wavebands were located in near infrared and red edge spectral regions. In conclusion, our results emphasize the potential benefits of the Sentinel-2 mission for agricultural applications
Phillip Lai: group exhibition (Hong Kong, 2017)
No full textGroup exhibition including artists He Yida (b. 1980, China), Handiwirman Saputra (b. 1975, Indonesia), Jeremy Everett (b. 1979, USA), Tao Hui (b. 1987, China) and Phillip Lai (b. 1969, Malaysia / UK
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Optical instruments for measuring leaf area index in low vegetation : application in Arctic ecosystems
No full textAuthor Posting. © Ecological Society of America, 2005. This article is posted here by permission of Ecological Society of America for personal use, not for redistribution. The definitive version was published in Ecological Applications 15 (2005): 1462–1470, doi:10.1890/03-5354.Leaf area index (LAI) is a powerful diagnostic of plant productivity. Despite the fact that many methods have been developed to quantify LAI, both directly and indirectly, leaf area index remains difficult to quantify accurately, owing to large spatial and temporal variability. The gap-fraction technique is widely used to estimate the LAI indirectly. However, for low-stature vegetation, the gap-fraction sensor either cannot get totally underneath the plant canopy, thereby missing part of the leaf area present, or is too close to the individual leaves of the canopy, which leads to a large distortion of the LAI estimate. We set out to develop a methodology for easy and accurate nondestructive assessment of the variability of LAI in low-stature vegetation. We developed and tested the methodology in an arctic landscape close to Abisko, Sweden.
The LAI of arctic vegetation could be estimated accurately and rapidly by combining field measurements of canopy reflectance (NDVI) and light penetration through the canopy (gap-fraction analysis using a LI-COR LAI-2000). By combining the two methodologies, the limitations of each could be circumvented, and a significantly increased accuracy of the LAI estimates was obtained. The combination of an NDVI sensor for sparser vegetation and a LAI-2000 for denser vegetation could explain 81% of the variance of LAI measured by destructive harvest. We used the method to quantify the spatial variability and the associated uncertainty of leaf area index in a small catchment area.This research was funded by U.S. National Science Foundation
grant DEB0087046
Dispelling the Myths Behind First-author Citation Counts
No full textWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
Estimation of leaf area index from PROBA/CHRIS hyperspectral multi-angular data
No full textLeaf Area Index (LAI) is a key structural and functional biophysical variable of the vegetated surfaces which is important in quantifying evapotranspiration rates and the energy exchange of terrestrial vegetation. Remote sensing offers a method of providing estimates of LAI through the analysis of the Bidirectional Reflectance Distribution Function (BRDF), an angular-dependent surface response. High-resolution, multi-angular and hyperspectral image data from PROBA/CHRIS (Project On-Board Autonomy/ Compact High Resolution Imaging Spectrometer) are used to estimate LAI. The retrieval of LAI is accomplished using the 1D turbid-medium canopy reflectance model, SAIL, coupled with the leaf reflectance model, PROSPECT REDUX. Look-up-tables are generated using scene-specific parameters required to invert the physically based model. Two experiments are performed to examine the contribution of multispectral versus hyperspectral reflectances (nadir direction) and single-look versus multi-look hyperspectral reflectances in deriving the LAI. Image data of the calibration/validation site at Chilbolton, Hampshire, UK are used for the inversion. In addition, ground measurements of LAI are compared with the retrieved LAI estimates. Retrieved LAI estimates using various spectral and directional sampling suggest that the spectro-directional reflectances from CHRIS provides more accurate results than their lower-resolution counterparts such as single-look and multispectral reflectances
MODIS Collection 6 global 8-daily LAI and FAPAR
No full textAbstract: Original LAI and FAPAR data (see https://lpdaac.usgs.gov/products/mod15a2hv006/) are read together with their bit-encoded quality information from the HDF-files. The quality information is decoded and provided in form of separate flag layers in addition to the LAI and FAPAR data for each tile of the MODIS sinusoidal grid in netCDF file format (see https://icdc.cen.uni-hamburg.de/en/modis-lai-fpar.html). These are subsequently read and re-gridded onto an equi-rectangular climate modeling grid (CMG). Only those LAI and FAPAR values are used where i) the cloud flag indicates a maximum of two cloud influences, and where ii) cloud cover is clearly defined, i.e. "assumed clear sky" is not used. Flag layers are summarized such that there is gridded information about 1) cloud fraction, 2) fraction of average and high aerosol load, 3) primary and secondary land-cover type, and 4) primary and secondary quality flag. Primary and secondary refer to the highest and 2nd-highest pixel count of the respective type or flag within the grid cell. Note that the count of valid values differs for the grid cell mean LAI and FAPAR and their variance, and for the grid-cell mean retrieval standard deviation.
TableOfContents: Grid cell mean FAPAR; Grid cell mean LAI; FAPAR variance across grid cell; LAI variance across grid cell; Grid cell mean FAPAR retrieval standard deviation; Grid cel mean LAI retrieval standard deviation; Count of useful FAPAR or LAI values per grid cell; Count of useful FAPAR or LAI retrieval standard deviation values in grid cell; Primary quality flag; Secondary quality flag; Primary land cover; Secondary land cover; Grid cell cloud fraction; Grid cell aerosol fraction
Technical Info: dimension: 720 columns x 360 rows x unlimited; temporalExtent_startDate: 2000-02-18; temporalExtent_endDate: 2020-12-31; temporalResolution: 8-daily; spatialResolution: 0.5; spatialResolutionUnit: degrees; horizontalResolutionXdirection: 0.5; horizontalResolutionXdirectionUnit: degrees; horizontalResolutionYdirection: 0.5; horizontalResolutionYdirectionUnit: degrees; verticalResolution: none; verticalResolutionUnit: none; verticalStart: none; verticalEnd: none; instrumentName: MODerate Resolution Spectroradiometer (MODIS); instrumentType: visible_to_infrared_spectroradiometer; instrumentLocation: Earth Observation Satellite (EOS) Terra; instrumentProvider: NOAA/NASA
Methods: [1] MODIS collection 6 (C6) LAI/FPAR Product User Guide, 24-February-2015, https://lpdaac.usgs.gov/sites/default/files/public/product_documentation/mod15_user_guide.pdf; [2] Myneni, R. B., et al., Algorithm Theoretical Basis Document (ATBD), v4.0, http://modis.gsfc.nasa.gov/data/atbd/atbd_mod15.pdf; [3] Yang, et al., From validation to algorithm improvement. Trans. Geosci. Rem. Sens., 44, 1885-1898, 2006; [4] Morisette, et al., Validation of global moderate resolution LAI products: A framework proposed within the CEOS Land Product Validation subgroup, Trans. Geosci. Rem. Sens., 44, 1804-1817, 2006; [5] Garrigues, et al., Validation and intercomparison of global Leaf Area Index products derived from remote sensing data, J. Geophys. Res., 113, G02028, https://doi.org/10.1029/2007JG000635, 2008; [6] https://icdc.cen.uni-hamburg.de/en/modis-lai-fpar.html
Units: Units for all variables (see TableOfContents): percent, m2/m2, percent, m4/m4, percent, m2/m2, 1, 1, 1, 1, 1, 1, percent, percent
geoLocations: westBoundLongitude: -180.0 degrees East; eastBoundLongitude: 180.0 degrees East; southBoundLatitude: -90.0 degrees North; northBoundLatitude: 90.0 degrees North; geoLocationPlace: global on land
Size: (files are packed into one zip-file per year)
2000: 40 files, 10901824 byte / file
2001-2018: 46 files / year, 10901824 byte / file
2019: 46 files, 10901856 byte / file
2020: 46 files, 10902528 byte / file
Format: netCDF
DataSources:
Original data on sinusoidal grid tiles in hdf-format: https://doi.org/10.5067/MODIS/MOD15A2H.006 [last access: 2021-01-12], see also: https://lpdaac.usgs.gov/products/mod15a2hv006/ [last access: 2021-01-26]
Data on sinusoidal grid tiles in netCDF-format: https://icdc.cen.uni-hamburg.de/en/modis-lai-fpar.html [last access: 2021-01-26]
Contact: stefan.kern (at) uni-hamburg.de
Web page: https://icdc.cen.uni-hamburg.de/en/modis-lai-fpar.html [last access: 2021-01-27
Chemical synthesis of LAI-1 and amino-LAI-1.
No full text<p>The chemical synthesis of the putative <i>L</i>. <i>pneumophila</i> small molecule compounds (A) LAI-1 and (B) amino-LAI-1 is shown.</p
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