High-resolution DEM generated from LiDAR data for water resource management

Terrain patterns play an important role in determining the nature of water resources and related hydrological modelling. Digital Elevation Models (DEMs), offering an efficient way to represent ground surface, allow automated direct extraction of hydrological features (Garbrecht and Martz, 1999), thus bringing advantages in terms of processing efficiency, cost effectiveness, and accuracy assessment, compared with traditional methods based on topographic maps, field surveys, or photographic interpretations. However, researchers have found that DEM quality and resolution affect the accuracy of any extracted hydrological features (Kenward et al., 2000). Therefore, DEM quality and resolution must be specified according to the nature and application of the hydrological features. The most commonly used DEM in Victoria, Australia is Vicmap Elevation delivered by the Land Victoria, Department of Sustainability and Environment. It was produced by using elevation data mainly derived from existing contour map at a scale of 1:25,000 and digital stereo capture, providing a state-wide terrain surface representation with a horizontal resolution of 20 metres. The claimed standard deviations, vertical and horizontal, are 5 metres and 10 metres respectively (Land- Victoria, 2002). In worst case, horizontal errors could be up to ±30m. Although high resolution stereo aerial photos provide a potential way to generate high resolution DEMs, under the limitations of currently used technologies by prevalent commercial photogrammetry software, only DSMs (Digital Surface Models) other than DEMs can be directly generated. Manual removal of the nonground data so that the DSM is transformed into a DEM is time consuming. Therefore, using stereo aerial photos to produce DEM with currently available techniques is not an accurate and costeffective method. Light Detection and Ranging (LiDAR) data covering 6900 km² of the Corangamite Catchment area of Victoria were collected over the period 19 July 2003 to 10 August 2003. It will be used to support a series of salinity and water management projects for the Corangamite Catchment Management Authority (CCMA). The DEM derived from the LiDAR data has a vertical accuracy of 0.5m and a horizontal accuracy of 1.5m. The high quality DEM leads to derive much detailed terrain and hydrological attributes with high accuracy. Available data sources of DEMs in a catchment management area were evaluated in this study, including the Vicmap DEM, a DEM generated from stereo aerial photos, and LiDAR-derived DEM. LiDAR technology and LiDAR derived DEM were described. In order to assess the capability of LiDAR-derived DEM for improving the quality of extracted hydrological features, sub-catchment boundaries and drainage networks were generated from the Vicmap DEM and the LiDAR-derived DEM. Results were compared and analysed in terms of accuracy and resolution of DEMs. Elevation differences between Vicmap and LiDAR-derived DEMs are significant, up to 65m in some areas. Subcatchment boundaries derived from these two DEMs are also quite different. In spite of using same resolution for the Vicmap DEM and the LiDARderived DEM, high accuracy LiDAR-derived DEM gave a detailed delineation of sub-catchment. Compared with results derived from LiDAR DEM, the drainage networks derived from Vicmap DEM do not give a detailed description, and even lead to discrepancies in some areas. It is demonstrated that a LiDAR-derived DEM with high accuracy and high resolution offers the capability of improving the quality of hydrological features extracted from DEMs

Photodissociation of complex nuclei at energies between the mesonic threshold and 1150 Mev

The photodisintegration of complex nuclei by gamma rays up to 1150 Mev has been studied by exposing nuclear emulsion to bremsstrahlung from the CalTech electron synchrotron and observing the "photostars" produced. Exposures were made at 16 different peak energies between 250 and 1150 Mev. Nearly 10 000 photostars were analyzed for star frequency, prong number, angular distribution, and (at 1143 Mev) the visible energy release per star. The bremsstrahlung yield of multiprong (≥2 prong) stars increases abruptly as photons capable of producing pions are included. The cross section per photon, derived from the bremsstrahlung yield by the photon difference method, is essentially constant at 250 microbarns/nucleon at all energies above 300 Mev. A model for photostar production is given which involves photopion production followed by absorption or scattering of the pion and recoil nucleon. Experimental free-nucleon photopion cross sections are used, together with the Monte Carlo calculations of Metropolis et al., to determine the probability for star formation. Good agreement with both the shape and magnitude of the excitation curve is obtained if nuclear motion is included. Mean and maximum prong numbers for photostars are the same as for stars produced by pions or protons of equal available energy. The mean-free-paths in nuclear matter of pions and protons are short, so that photostar yields are a measure of the integrated total photomeson cross section. More than 95% of the multiprong stars made by 1-Bev bremsstrahlung are made by photons whose energies exceed the pion production threshold of 150 Mev. Most of the 1-prong events are produced by photons below 150 Mev, and the yield is consistent with giant resonance (γ, p) reactions plus "pseudodeuteron" photodisintegration, a process whose cross section rapidly decreases as the photon energy increases. Variation of mean prong number with energy and comparison with nuclear cascade calculations suggests that the excitation of the residual nucleus is nearly constant at 100 Mev over a wide range of incident photon energies. The visible energy release per photostar shows a linear dependence on prong number, and more than half of the photon energy is carried away by neutral particles

What are the educational needs and experiences of asylum-seeking and refugee children, including those who are unaccompanied, with a particular focus on inclusion? - A literature review

In a context of mass displacement and flows of asylum-seeking and refugee peoples across national borders, the need to respond and attend to the education of asylum-seeking and refugee children is urgent and pressing, though it is not without its challenges. This literature review focuses on the educational experiences of asylum seeking and refugee children, including those who are unaccompanied, with a particular focus on inclusion. It seeks to respond to the following three interconnected questions: 1. What does current educational literature tell us about the educational needs and experiences of asylumseeking and refugee children as they relate to inclusion? 2. What does current educational literature tell us about the educational needs and experiences of unaccompanied asylum-seeking and refugee children as they relate to inclusion? 3. What implications and recommendations can be drawn from existing literature? The review has a particular interest in the needs and experiences of unaccompanied asylum-seeking and refugee children, but recognises that though there is a developing literature specifically on unaccompanied asylum seeking and refugee children (see, for example, Stanley, 2001; Derluyn and Broekaert, 2008; Pastoor, 2015) such needs must be understood and positioned in relation to the wider educational needs and experiences of asylum seeking and refugee children more generally. While other literature reviews on asylum-seeking and refugee children are available (see, for example, Hek, 2005; McBrien, 2005), the present review adds to existing work by: • including an explicit focus on the educational needs and experiences of asylum-seeking and refugee children who are unaccompanied; • providing an up-to-date review of literature which analyses and reports the educational needs and experiences of asylum-seeking and refugee children. The review focuses in particular on post-migration experiences within school settings as they relate to asylum seeking and refugee children’s social inclusion

Inclusive educational provision for newly-arrived unaccompanied asylum-seeking and refugee children: a study in a single school in Kent

Recent migration flows – including those resulting from conflict, persecution and natural disaster – place a responsibility on nations to honour international and humanitarian commitments with respect to refugees. A central part of these commitments is to make provision for the educational needs of asylum-seeking and refugee children, including those whom are unaccompanied. Indeed, education and schooling play a crucial role in the complex relationship between newly-arrived immigrants and their new host communities. In the UK and elsewhere a body of research evidence has developed regarding the post-migration educational needs and experiences of asylum-seeking and refugee children. As we have reported elsewhere (Peterson et al., 2016), such research points to a range of approaches, relationships and practices through which asylum-seeking and refugee children are, and indeed at times are not, included within their new communities, including the school community. The study reported here was conducted in a national and local context of increased recognition (both positive and negative) of the humanitarian plight and presence of asylum-seeking and refugee people and children, including children whom are unaccompanied. The study focused on the approach of a single 11-18 school –Hartsdown Academy – situated in Margate, Kent. Working with Virtual School Kent, the school has developed its existing educational provision to include newly-arrived unaccompanied asylum-seeking and refugee children. The present study is concerned particularly with the perceived and actual social and cultural outcomes and benefits (including any notable challenges and barriers) of the school’s approach to including newly-arrived unaccompanied asylum-seeking and refugee children

Fractional quantum Hall effects in bilayers in the presence of inter-layer tunneling and charge imbalance

Two-component fractional quantum Hall systems are providing a major motivation for a large section of the physics community. Here we study two-component fractional quantum Hall systems in the spin-polarized half-filled lowest Landau level (filling factor 1/2) and second Landau level (filling factor 5/2) with exact diagonalization utilizing both the spherical and torus geometries. The two distinct two-component systems we consider are the true bilayer and effective bilayers (wide-quantum-well). In each model (bilayer and wide-quantum-well) we completely take into account inter-layer tunneling and charge imbalancing terms. We find that in the half-filled lowest Landau level, the FQHE is described by the two-component Abelian Halperin 331 state which is remarkably robust to charge imbalancing. In the half-filled second Landau, we find that the FQHE is likely described by the non-Abelian Moore-Read Pfaffian state which is also quite robust to charge imbalancing. Furthermore, we suggest the possibility of experimentally tuning from an Abelian to non-Abelian FQHE state in the second Landau level, and comment on recent experimental studies of FQHE in wide quantum well structures.Comment: 25 pages, 27 figure

A Partner Evokes Latent Differences between Hox Proteins

Hox transcription factors bind highly related DNA sequences in vitro, yet they regulate different genes and play distinct roles in anterior-posterior patterning in animals. Slattery et al. report that a common cofactor, Exd, accentuates latent sequence specificities of all eight Hox proteins and directs binding to relevant sites across the genome

The influence of structural defects on intra-granular critical currents of bulk MgB2

Bulk MgB2 samples were prepared under different synthesis conditions and analyzed by scanning and transmission electron microscopy. The critical current densities were determined from the magnetization versus magnetic field curves of bulk and powder-dispersed-in-epoxy samples. Results show that through a slow cooling process, the oxygen dissolved in bulk MgB2 at high synthesis temperatures can segregate and form nanometer-sized coherent precipitates of Mg(B,O)2 in the MgB2 matrix. Magnetization measurements indicate that these precipitates act as effective flux pinning centers and therefore significantly improve the intra-grain critical current density and its field dependence.Comment: 4 pages, 4 figures, to be published in IEE Transactions in Applied Superconductivit

Uncovering Elementary Teachers\u27 Notions of Engineering Design Practices using Video-Captured Instruction

This article describes a 3-credit STEM education graduate course that provided knowledge and experiences to elementary school teachers for incorporating engineering design process (EDP) into their instruction. We analyzed teacher\u27s written reflections that gave us insights to the successes and challenges in helping teachers develop their notions and implementation of the EDP

The effect of LiDAR data density on DEM accuracy

Digital Elevation Models (DEMs) play an important role in terrain related applications, and their accuracy is crucial for DEM applications. There are many factors that affect the accuracy of DEMs, with the main factors including the accuracy, density and distribution of the source data, the interpolation algorithm, and the DEM resolution. Generally speaking, the more accurate and the denser the sampled terrain data are, the more accurate the produced DEM will be. Traditional methods such as field surveying and photogrammetry can yield high accuracy terrain data, but are very time consuming and labour intensive. Moreover, in some situations such as in densely forested areas, it is impossible to use these methods for collecting elevation data. Light Detection and Ranging (LiDAR) offers high density data capture. The high accuracy three dimensional terrain points prerequisite to very detailed high resolution DEMs generation offers exciting prospects to DEM builders. However, because there is no sampling density selection for different area during a LiDAR data collection mission, some terrains may be oversampled thereby imposing increases in data storage requirements and processing time. Improved efficiency in these terms can accrue if redundant data can be identified and eliminated from the input data set. With a reduction in data, a more manageable and operationally sized terrain dataset for DEM generation is possible (Anderson et al., 2005a). The primary objective of data reduction is to achieve an optimum balance between density of sampling and volume of data, hence optimizing cost of data collection (Robinson, 1994). Some studies on terrain data reduction have been conducted based on the analysis of the effects of data reduction on the accuracy of DEMs and derived terrain attributes. For example, Anderson et al. (2005b) evaluated the effects of LiDAR data density on the production of DEM at different resolution. They produced a series of DEMs at different horizontal resolutions along a LiDAR point-density gradient, and then compared each of these DEMs to a reference DEM produced from the original LiDAR data, this having been acquired at the highest available density. Their results showed that higher resolution DEM generation is more sensitive to data density than is lower resolution DEM generation. It was also demonstrated that LiDAR datasets could withstand substantial data reductions yet still maintain adequate accuracy for elevation predictions (Anderson et al., 2005a) This study explored the effects of LiDAR point density on DEM accuracy and examined to scope for data volume reduction compatible with maintaining efficiency in data storage and processing. Something of the relationship between data density, data file size, and processing time also emerges from this study