RAST: finding related documents based on triplet similarity

With the increasing amount of information available in recent years, searching for the desired content is becoming a challenging task. In this work, a tool for searching abstracts submitted to scientific conferences is introduced. It not only searches abstracts by the given keyword(s) but also displays abstracts related to a single or multiple selection. It also displays highly relevant abstracts together with possible keywords to help users refine their search. Analysis of the conditional similarity algorithm proposed here has shown that it does provide better output compared to ordinary cosine similarity, as well as the list of possible keywords reflects results of latent topic analysis. An interface for storing and sorting selected abstracts for future review and/or printing is also provided.     

Electronic band-edge properties of rock salt PbY and SnY (Y= S, Se, and Te)

The electronic band-edges of lead chalcogenides PbY and tin chalcogenides SnY (where Y = S, Se, and Te) are investigated by the means of a full-potential linearized augmented plane wave (FPLAPW) method and the local density approximation (LDA). All six chalcogenide binaries have similar electronic structures and density-of-states, but there are differences in the symmetry of the band-edge states at and near the Brillouin zone L-point. These differences give the characteristic composition, pressure, and temperature dependences of the energy gap in Pb_1−xSn_xY alloys.We find that: (1) SnY are zero-gap semiconductors E_g = 0 if the spin–orbit (SO) interaction is excluded. The reason for this is that the conduction band (CB) and the valence band (VB) cross along the Q ≡ LW line. (2) Including the SO interaction splits this crossing and creates a direct gap along the Q-line, thus away from the L symmetry point. Hence, the fundamental band gap E_g in SnY is induced by the SO interaction and the energy gap is rather small E_g ≈ 0.2–0.3 eV. At the L-point, the CB state has symmetric and the VB state is antisymmetric thereby the L-point pressure coefficient ∂E_g(L)/∂p is a positive quantity. (3) PbY have a direct band gap at the L-point both when SO coupling is excluded and included. In contrast to SnY, the SO interaction decreases the gap energy in PbY. (4) Including the SO interaction, the LDA yields incorrect symmetries of the band-edge states at the L-point; the CB state has and the VB state has symmetry. However, a small increase of the cell volume corrects this LDA failure, producing an antisymmetric CB state and a symmetric VB state, and thereby also yields the characteristic negative pressure coefficient ∂E_g(L)/∂p in agreement with experimental findings. (5) Although PbY and SnY have different band-edge physics at their respective equilibrium lattice constants, the change of the band-edges with respect to cell volume is qualitatively the same for all six chalcogenides. (6) Finally, in the discussion of the symmetry of the band edges, it is important to clearly state the chosen unit cell origin; a shift by (a/2,0,0) changes the labeling of the irreducible representations.     

Numerical and experimental analysis of microstructure formation during stainless steels solidification

The aim of this work is to examine microstructure formation during the solidification of unidirectional solidified AISI 304 stainless steel. Numerical and experimental results indicate that this numerical model allows a precise analysis of the AISI 304 stainless steel microstructure formation. This model determines temperature profiles, position of liquid and solid isotherms, thermal parameters (thermal gradients, tip rate movement, rate cooling), and finally, the secondary inter dendritic spacing. This model was tested by comparing the experimental values results, and thus a reasonable correlation was found.     

The Role of Regulation in Meeting Water Demands under Climate Change

The satisfaction of water demands in semi-arid regions could be affected as a consequence of climate change. In this study, the impact due to future climate scenarios in the Chira and Piura basins located in northern Peru was evaluated. Two indicators, the demand satisfaction index (I₁) and the demand reliability index (I_2p), were used to analyze water scarcity problems. An analysis of the basins by region highlighted the importance of regulation infrastructure in minimizing the effects of climate change to meet water demands.     

Multifilter rotating shadowband radiometer calibration for spectral aerosol optical depth retrievals over S?o Paulo City, Brazil

Multifilter rotating shadowband radiometer (MFRSR) calibration values for aerosol optical depth (AOD) retrievals were determined by means of the general method formulated by Forgan [Appl. Opt.33, 4841 (1994)] at a polluted urban site. The obtained precision is comparable with the classical method, the Langley plot, applied on clean mountaintops distant of pollution sources. The AOD retrieved over S?o Paulo City with both calibration procedures is compared with the Aerosol Robotic Network data. The observed results are similar, and, except for the shortest wavelength (415 nm), the MFRSR's AOD is systematically overestimated by approximately 0.03.     

Strained and strain-balanced quantum well devices for high-efficiency tandem solar cells

The state of GaAs/InGaAs quantum well solar cell research is reviewed. The effect of strain upon the GaAs/InGaAs cells is discussed and the limits to a strained GaAs/InGaAs cell established. The strain-balance approach is suggested as a means of overcoming the limits inherent to the strained approach and the principle is demonstrated in two differing device configurations. The strain-balance devices show enhanced efficiencies over their strained counterparts and in one case, comparable efficiency to a good GaAs control cell. The application of these cells to tandem structures is discussed, indicating the potential for a substantial efficiency enhancement.     

Study of degradation mechanisms in compound semiconductor based devices by SEM-cathodoluminescence

This papers reports on the microcharacterization of devices for optoelectronic and high-speed electronic applications by spectrally resolved cathodoluminescence. The advantages offered by the high lateral resolution, monochromatic imaging and depth resolved spectral analysis of the technique are presented. In particular, Inp based semiconducting optical amplifiers and GaAs based pump lasers for optical fiber communications are characterized from the point of view of compositional inhomogeneities and defect generation in the active regions. GaAs based heterojunction bipolar transistors and high electron mobility transitors are studied to respectively reveal Be outdiffusion from the base and break down walkout after bias aging. GaAs based solar cells are also investigated to show the correlation between dislocations and impurity gettering. Finally the limits of the technique are briefly discussed.     

Hydrogen transport vapor phase epitaxy of CdTe on hybrid substrates for x-ray detector applications

The growth of thick CdTe epitaxial layers by the hydrogen transport vapor phase epitaxy (H₂T-VPE) method is reported for the first time. The thermodynamics of the H₂ transport method of CdTe is analyzed to determine the equilibrium partial pressures of the molecular species in the vapor and its supersaturation as a function of growth conditions. (100)-oriented CdTe epilayers are successfully grown by H₂T-VPE on hybrid ZnTe/GaAs(100) substrates prepared by metalorganic vapor phase epitaxy. Growth rates up to 10 μm/h are obtained at temperatures ∼760°C and with the CdTe source temperature at 827°C. The achievement of even higher growth rates can be foreseen by using the present method under slightly different conditions; several hundreds micron thick CdTe layers can be thus grown by the H₂T-VPE. CdTe samples have mirror-like, nearly featureless surfaces. Also, CdTe epilayers have shown a medium-to-high resistivity at room temperature, possibly as a result of compensation by donor impurities diffusing from GaAs. Still the growth of highly resistive layers by in-situ chlorine doping during the H₂T-VPE growth is possible. In summary, H₂T-VPE is a potential alternative to traditional melt- and vapor-growth methods for the synthesis of detector-grade CdTe for application to the 1–100 keV x-ray energy range.     

Yield Analysis of Oil Palm Cultivated Under Irrigation in the Brazilian Savanna

The oil palm is currently a major source of oil used worldwide for biofuel production and food. In Brazil, it is grown in high rainfall and high temperature regions. The high cost of this oil crop in the Brazilian Amazonia, combined with environmental and land ownership issues and the occurrence of diseases, has aroused considerable interest in growing it in other regions of the country, including the Savanna (Cerrado) Biome. This study aimed to evaluate, for 1 year, the fruit bunch, the oil yield, and other parameters of two oil palm cultivars (BRS C1001 and BRS C2501) under the typical Savanna conditions in the Federal District, Brazil. Differences between these cultivars were observed in some parameters evaluated throughout the year (p < 0.05). The oil yield/bunch ranged from 25 to 32 and 29 to 36 % for BRS C2501 and BRS C1001 cultivars, respectively and similar to those obtained for the same cultivars in the Brazilian Amazonia and for other genotypes in Indonesia, Sumatra, and Malaysia. Both cultivars proved to be promising in terms of oil yield in a trail carried out at 1000 m of altitude under irrigation at Cerrado Biome in Brazil.