Observation of Ga droplet formation on (311)A and (511)A GaAs surfaces

Using (100) GaAs substrates as a reference, we present a study of the formation of Ga droplets on (311)A and (511)A GaAs substrates in which the effect of both the substrate temperature and the amount of Ga supplied on the droplet density and height for the three different surfaces have been investigated. Droplets on (100) substrates show a round shape; however, they appear as elongated balls with tails along the [Formula: see text] direction of the (311)A substrate and the [Formula: see text] direction of the (511)A substrate. It has been found that the Ga droplets on (511)A surfaces have lower densities and higher heights than those on (100) substrates. In contrast, Ga droplets on (311)A surfaces have lower heights and much higher densities compared to those for both (100) and (511)A. We observed that the decrease in the droplet density with increasing growth temperature for both (311)A and (511)A is more than twice that for the (100)GaAs surface due to the larger drop in the nucleation rate. Based on these observations, we offer a physical explanation based on the thermodynamics and the anisotropy of the high-index surfaces.     

Thermo-solutal-diffusion in high pressure liquid mixtures in the presence of micro-vibrations

Computational Fluid Dynamics simulations of the thermodiffusion in high pressure ternary hydrocarbon mixtures of methane, n-butane and n-dodecane subject to micro-vibrations at reduced gravity are presented. Micro-gravity investigations of mixtures at such high pressures are unprecedented. The simulations indicate a formation of a single convective cell in all the mixtures due to a steady static micro-gravity in the x and y directions, and a stronger velocity component orthogonal to the direction of the temperature gradient. The consequent separation behavior of methane and n-dodecane in terms of the concentration profiles as well as the thermodiffusion coefficients was in agreement with the experimental trends. Also, as in the experiments, the change in the sign of the thermodiffusion coefficient of n-butane was correctly predicted. Small discrepancy was observed in the concentration profile of n-butane and is due to the under prediction of the thermodiffusion coefficients by the current thermodiffusion model as well as the displacement of small traces of n-butane via the bulk flow of n-dodecane.     

Disturbance Evaluation in Power System Based on Machine Learning

The operation complexity of the distribution system increases as a large number of distributed generators (DG) and electric vehicles were introduced, resulting in higher demands for fast online reactive power optimization. In a power system, the characteristic selection criteria for power quality disturbance classification are not universal. The classification effect and efficiency needs to be improved, as does the generalization potential. In order to categorize the quality in the power signal disturbance, this paper proposes a multi-layer severe learning computer auto-encoder to optimize the input weights and extract the characteristics of electric power quality disturbances. Then, a multi-label classification algorithm based on rating is proposed to understand the relationship between the labels and identify the various power quality disturbances. The two algorithms are combined to construct a multi-label classification model based on a multi-level extreme learning machine, and the optimal network structure of the multi-level extreme learning machine as well as the optimal multi-label classification threshold are developed. The proposed method can be used to classify the single and compound power quality disturbances with improved classification effect, reliability, robustness, and anti-noise performance, according to the experimental results. The hamming loss obtained by the proposed algorithm is about 0.17 whereas ML-RBF, SVM and ML-KNN schemes have 0.28, 0.23 and 0.22 respectively at a noise intensity of 20 dB. The average precision obtained by the proposed algorithm 0.85 whereas the ML-RBF, SVM and ML-KNN schemes indicates 0.7, 0.77 and 0.78 respectively.     

Interactions between color and word processing in a flanker task.

To examine interactions between color and word attributes, participants responded, either manually or vocally, to a central target (color patch or word) flanked by a Stroop stimulus. Color and word attributes of the flanker affected both vocal and manual responding to color patches. Color and word flankers also affected manual responding to word targets, but only word flanker affected vocal responding to word targets. These results are not consistent with models (e.g., translational models) of Stroop tasks, which posit that interactions between colors and words occur only when vocal responding is required. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

European Bronze Age Sheet Metal Objects: 3,000 Years of High-Level Bronze Manufacture

This article focuses on the manufacture and usage of selected sheet metal objects from helmets, a vessel, and two shields from the European Bronze Age and Early Iron Age, which date from the thirteenth to seventh centuries BC. Manufacturing traces on the surface, as well as metallographic investigations and the analyses of the alloy composition with scanning electron microscope–energy-dispersive x-ray spectroscopy, provided an insight into the manufacturing techniques and the production of valuable, high-status objects, and highlighted the potential changes in manufacturing techniques and alloys used during different time periods.     

Spatial analysis of urban stormwater quality: Ramallah district as a case study, Palestine

Urban runoff pollution sources are formidable obstacles to achieving water source goals in numerous municipalities. Ramallah district currently holds one of the highest rates of urbanization in Palestine causing a significant increase in surface runoff. Consequently, this causes increased flooding and a significant decrease in water quality due primarily to the accumulation of pollutants. To date, most research has focused on specifying temporal variations of stormwater quality parameters that include high uncertainties and also increase the risk of pollution control structures' failure. Spatial variations of the runoff quality are the key factor in nonpoint source pollution studies. This research investigates the spatial variability of urban runoff quality parameters in relation to land use of urban catchments. The research estimated pollutant concentration for improved and efficient design of pollution control structures for each land use.     

Technical note an evaluation of water corrosivity of the river tigris at Baghdad

A series of experiments was carried out on different samples of tap water abstracted from the Baghdad water supply network in order to observe the effect of water on supply pipes, either scale forming or corrosive. This experimental investigation on the corrosive effect of the city of Baghdad tap water showed that the water can be classified as corrosive according to the Ryznar index, while the Langelier index showed that the water has the ability to form scale on the pipes. However, personal field observation indicated that the water is corrosive to the pipes and to the network appurtenance. Other findings are reported herein.