Assessment of Digital Elevation Model (DEM) aggregation methods for hydrological modeling: Lake Chad basin,Africa

Digital Elevation Models (DEMs) are used to compute the hydro-geomorphological variables required by distributed hydrological models. However, the resolution of the most precise DEMs is too fine to run these models over regional watersheds. DEMs therefore need to be aggregated to coarser resolutions, affecting both the representation of the land surface and the hydrological simulations. In the present paper, six algorithms (mean, median, mode, nearest neighbour, maximum and minimum) are used to aggregate the Shuttle Radar Topography Mission (SRTM) DEM from 3″ (90 m) to 5′ (10 km) in order to simulate the water balance of the Lake Chad basin (2.5 Mkm²). Each of these methods is assessed with respect to selected hydro-geomorphological properties that influence Terrestrial Hydrology Model with Biogeochemistry (THMB) simulations, namely the drainage network, the Lake Chad bottom topography and the floodplain extent.The results show that mean and median methods produce a smoother representation of the topography. This smoothing involves the removing of the depressions governing the floodplain dynamics (floodplain area<5000 km²) but it eliminates the spikes and wells responsible for deviations regarding the drainage network. By contrast, using other aggregation methods, a rougher relief representation enables the simulation of a higher floodplain area (>14,000 km² with the maximum or nearest neighbour) but results in anomalies concerning the drainage network. An aggregation procedure based on a variographic analysis of the SRTM data is therefore suggested. This consists of preliminary filtering of the 3″ DEM in order to smooth spikes and wells, then resampling to 5′ via the nearest neighbour method so as to preserve the representation of depressions. With the resulting DEM, the drainage network, the Lake Chad bathymetric curves and the simulated floodplain hydrology are consistent with the observations (3% underestimation for simulated evaporation volumes).     

Postgraduate occupations of psychology major students.

During the last ten or fifteen years we have seen an increase in enrollment in undergraduate psychology courses that is far out of proportion to the general increase in overall university attendance. Psychology departments are overwhelmed with undergraduate students, and the numbers continue to increase each year. Since we are allocating so much of our time, energy, and resources to undergraduate teaching, it is important to determine what these students are being educated for. This note reports the results of an inquiry into the postgraduate occupations of the members of the first three graduating classes of the psychology major programme at McGill University. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Fabrication and performance of InP-based heterostructure barriervaractors in a 250-GHz waveguide tripler

High-performance InGaAs-InAlAs-AlAs heterostructure barrier varactors (HBV's) have been designed, fabricated, and RF tested in a 250-GHz tripler block. The devices with two barriers stacked on the same epitaxy are planar integrated with coaxial-, coplanar-, and strip-type configurations. They exhibit state-of-the-art capacitance voltage characteristics with a zero-bias capacitance C₃⁰ of 1 fF/μm² and a capacitance ratio of 6:1. Experiments in a waveguide tripler mount show a 9.8-dBm (9.55-mW) output power for 10.7% conversion efficiency at 247.5 GHz. This is the highest output power and efficiency reported from an HBV device at J-band (220-325 GHz)     

A tale of two tails.

Comments on A. Feingold's (see record 1995-15953-001) claim that one cannot have an accurate image of group comparisons by looking only at mean difference and effect size, d. This is because, if the comparison groups have differenct variances, the differences in the left and right tails are not symmetrical and must be calculated separately using the variances of each distribution to estimate the relative tail weights at any given z. Feingold is commended for recognizing that tail differences must be examined separatetly, however, there is an assumption that it is possible to establish a standard formula for all comparisons. Although Feingold's contribution is not without merit, it hs the double flaw of resting on a questionable assumption of normality, and of, remaining insenstive to important aspects of data. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Antioxidant potency of highly purified polyepicatechin fractions

The purpose of this study was to characterise the purified fractions of the novel highly stable polymer polyepicatechin and test them for their antioxidant potency. This paper presents, for the first time, a methodology for separating the fractions for food applications. Polyepicatechin is synthesised, using Green chemistry, through the enzymatic polymerisation, in a water/ethanol mixture of epicatechin (a flavonol found in green tea). The polyepicatechin, which is entirely different from the natural proanthocyanidin, is soluble in a water/ethanol mixture. The ultimate objective is to increase the thermal stability and antioxidant potency of epicatechin so it can be applied to foods, such as poultry and fish, to reduce their rancidity. UV–Vis, FTIR, MS–MS and NMR were used to deduce certain aspects of the structure, and the experimental work was combined with computational modeling. The results show polyepicatechin gives a preferable site of reaction via-resorcinol and the lowest polar fraction shows higher antioxidant potency compared to tert-butylhydroquinone (TBHQ). The next step is to assess the enzyme inhibition and anticancer potency of these fractions.     

Design of a 45° incidence millimeter wave diplexer

The design of a 45° incidence millimeter wave radiometer diplexer is described. Experimental data are presented that are in good agreement with the theoretical predictions.     

Is academic freedom in peril?

Comments on the articles of J. J. Furedy (see record 199801996-002), H. J. Klatt (see record 199801996-004), C. Stark (see record 199801996-005), D. Kimura (see record 199801996-006), and K. S. Dobson (see record 199801996-007), on the multifaceted topics surrounding political correctness in academia, including academic freedom, and women's issues. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A novel Computer-Aided Tree Species Identification method based on Burst Wind Segmentation of 3D bark textures

Terrestrial Laser Scanning (TLS) systems have gained increasing popularity in the forestry domain and are today widely used for the automatic measurement of forest inventory attributes. Nevertheless, to the best of our knowledge the problem of tree species recognition from TLS data has received very little attention from the scientific community. It is in this context that we present a novel Computer-Aided Tree Species Identification method based on 3D bark texture analysis. The novelty of our approach resides in the following three key points: (1) 3D salient regions extraction using a new morphological segmentation method that we have called Burst Wind Segmentation, (2) the extraction and pre-annotation of a collection of typical 3D bark patterns, known as scars, from each of the tree species. The pre-annotated scars are stored in a dictionary that we have called ScarBook and they are used as a reference for the comparison of the 3D salient segmented regions, (3) a wide variety of advanced shape, saliency, curvature and roughness features are extracted from the 3D salient segmented regions. To study the performance of our method, an experiment has been carried out on a dataset composed of 969 patches which correspond to 30 cm long segments of the trunk at breast height. Six species among the most dominant species in European forests have been tested with patches of different diameter at breast height values so as to study the identification accuracy with respect to age. The results obtained are very encouraging and promising and they confirm the possibility of identifying tree species using TLS data.     

Four-Element Receiver for Pulsed 10-mum Heterodyne Doppler Lidar

A four-element photomixer receiver has been tested in a 10-mum heterodyne Doppler lidar. It addresses a reduction of the variance of the power scattered off distributed aerosols targets at ranges as long as 8 km. An improvement in performance is expected when the four independent signals recorded on every single shot are combined. Two summation techniques of the four signals have been implemented: a coherent summation of signal amplitude and an incoherent summation of intensities. A phasing technique for the four signals is proposed. It is based on a more suitable correlation time with discernible self-consistent packets (SCP's). The SCP technique has been successfully tested, and the results obtained with a coherent summation of the four signals, i.e., variance reduction, carrier-to-noise ratio improvement, and velocity accuracy improvement, are in agreement with theory.     

Evaluating political correctness: Anecdotes vs. research.

"Political correctness", by being linked with anecdotal accounts of some extreme incidents, has become an epithet which is used by conservatives to discredit left-liberal policies, while conservative measures, which themselves endanger some of the most valuable academic traditions, are presented as economically necessary and inevitable. An even-handed evaluation of political influences on universities must abandon the anecdotal for a comprehensive examination of the overall positive and negative influences of all policies, regardless of their political colouration. Left-liberal and conservative policies are examined and compared in the contexts of women's studies, group difference research, affirmative action, and sexual harassment policies. (PsycINFO Database Record (c) 2010 APA, all rights reserved)