First Principles Calculation of Field Emission from Nanostructures using Time-Dependent Density Functional Theory: a Simplified Approach

We introduce a new simplified method for computing the electron field emission current in short carbon nanotubes using ab-initio computation in periodic simulation cells. We computed the evolution of the wave functions using Time-Dependent Density Functional Theory, where we have utilized the Crank-Nicholson propagator. We found that in pristine carbon nanotubes, the emitted charge tends to emerge mostly from electrons that are concentrated at the nanotube tip region. The charge beam concentrates into specific channel structures, showing the utility of carbon nanotubes in precision emission applications.Comment: Submitted to Physica

Development Of An Improved Microwave Ocean Surface Emissivity Radiative Transfer Model

An electromagnetic model is developed for predicting the microwave blackbody emission from the ocean surface over a wide range of frequencies, incidence angles, and wind vector (speed and direction) for both horizontal and vertical polarizations. This ocean surface emissivity model is intended to be incorporated into an oceanic radiative transfer model to be used for microwave radiometric applications including geophysical retrievals over oceans. The model development is based on a collection of published ocean emissivity measurements obtained from satellites, aircraft, field experiments, and laboratory measurements. This dissertation presents the details of methods used in the ocean surface emissivity model development and comparisons with current emissivity models and aircraft radiometric measurements in hurricanes. Especially, this empirically derived ocean emissivity model relates changes in vertical and horizontal polarized ocean microwave brightness temperature measurements over a wide range of observation frequencies and incidence angles to physical roughness changes in the ocean surface, which are the result of the air/sea interaction with surface winds. Of primary importance are the Stepped Frequency Microwave Radiometer (SFMR) brightness temperature measurements from hurricane flights and independent measurements of surface wind speed that are used to define empirical relationships between C-band (4 - 7 GHz) microwave brightness temperature and surface wind speed. By employing statistical regression techniques, we develop a physical-based ocean emissivity model with empirical coefficients that depends on geophysical parameters, such as wind speed, wind direction, sea surface temperature, and observational parameters, such as electromagnetic frequency, electromagnetic polarization, and incidence angle

Subsurface thermal regime to delineate the paleo-groundwater flow system in an arid area, Al Kufra, Libya

AbstractThe purpose of this study was to understand the groundwater flow system in Al Kufra basin, Libya, as a case study of arid areas using subsurface temperature. The temperature-depth profiles and water levels were measured in eight boreholes in the area. Well 6 is considered a recharge type profile with low geothermal gradient (0.0068°C/m) and an estimated paleo-temperature around 19.5°C. The other profiles are of discharge type with higher geothermal gradient (0.0133 to 0.0166°C/m). The constructed horizontal 2D distribution maps of the hydraulic heads and the subsurface temperature measurements reveal that the main recharge area is located to the south with low temperature while the main discharge area is located to the north with higher temperature. Vertical 2D distribution maps show that location of well 4 has low hydraulic heads and higher temperature indicating that the fault defined in the area may have affected the groundwater flow system. The estimated groundwater flux ranges from 0.001 to 0.1mm/day for the recharge area and from −0.3 to −0.7mm/day in average in the discharge area

Petrography and Geochemistry of Lower Paleozoic Sandstone Sequence, Girvan

Detailed petrographic and geochemical investigations of the Girvan sandstones-grey wackes indicate a great range in petrography and geochemistry. In terms of petrography, the dominantly basic and ultrabasic-, lava-bearing (ophiolitic) greywackes at the base of the Girvan sequence (Upper Llanvirn-Llandeilo) are replaced upwards in the Caradoc-Ashgill by sandstones characterized by acid rock fragments which include lavas and detritus probably derived from high level plutonic intrusions. During the Silurian, however, the contributions from the mafic and ultramafic source have ceased completely, acid rock fragments had become scarce and most of the contributions to the basin was quartz-rich recycled orogenic detritus. The great heterogeneities in the greywacke composition and the systematic changes in petrography as summarized above, are in concert with the chemistry of 212 smples were chemically and modully analysed for all major and 12 trace elements The greywackes of all ages show very large chemical variations both in their major and trace elements but they exhibit progressive changes with younging age. Particularly Si, the incompatible elements, Rb, Ba and some REE increase to their highest values in passing from Upper Llanvirn through to Llandovery. In contrast, the compatible elements such as Mg, Ni, Co and Cr are enriched in the lower sequence and decrease systematically upwards. In terms of provenance areas and tectonic settings, despite some disagreements between the various models proposed, it is concluded that except for the Silurian rocks which were dominantly derived from recycled sediments, the Ordovician rocks were derived from a magmatic arc and deposited in a forearc or backarc region The chemistry also confirms a magmatic derivation of the greywackes and deposition in a forearc or backarc region Chemical re-investigations of the Southern Uplands greywackes show that these were also deposited in a proximal arc basins. Despite some differences in composition between the two areas, a paleogeographical linkage of Girvan to Southern Uplands is suggested and the previously thought backarc or allochthonous settings for the Southern Uplands is not supported by the data presented here

Management of annual reported income in the UK: the search for indicators

The main purpose of this research was to ascertain whether users of reported income are receiving measurement of past activity that is free from management bias.This research consisted of two major parts, namely the theoretical and the empirical.In the theoretical part, attempts were made: (i) to determine the roots of the theoretical propositions for empirical investigation and (ii) to examine, theoretically, the assertion that managers are able to manipulate reported results through acceptable accounting means.In this part, it was argued that managers of listed firns are more likely to smooth reported income and bias their accounting policies towards income-increasing methods, while managers of unlisted firms are more likely to bias their accounting policies towards income-decreasing methods. Also it was argued that managers are able to manipulate reported income through acceptable accounting means.In the empirical part, an attempt was made to determine the relative adherence of listed and unlisted firms to one of three reporting strategies, namely smoothing of, increase of anddecrease of reported income. In this regard, two principal hypotheses were developed and tested.The first hypothesis stated that the proportion of listed firms with relatively smooth income streams is significantly higher than that of unlisted firms. The empirical findings are consistent with this hypothesis for all objects of smoothing considered in this research. Furthermore, the results suggest that ordinary income is the most common object of smoothing among listed firms.The second hypothesis was that there is a significant difference in the means of the profitability rate between the two sets of firms.The empirical findings are consistent with this hypothesis. Also,, the magnitude and the direction of the differences in the profitability rates indicate that listed firms report higher profitability rates than unlisted firms and the observations of the profitability rates among listed firms are more concentrated around their means than those of unlisted firms.Based on the findings of this research, it is justifiable to conclude that users of reported income are receiving measurement of past activity that is not free from management bias

The determinants of citizens\u27 satisfaction in the water public service: the case study of the governorate of Fayoum

This empirical study aims at investigating the determinants that influence the level of citizens\u27 satisfaction regarding the water public service. It provides the policy makers and the management of the water companies, with scientific evidence on the factors that control the citizens\u27 satisfaction, and the potential areas of water service improvement. The study used a primary data from a survey of 3000 respondents, collected by the Social Contract Center in December 2011 in the governorate of Fayoum. The investigated variables of this study have been classified into two main groups; the first group is the service-related variables, which included variables related to the water quality, and service quality. The second group is the non service-related variables, which included the socioeconomic, and the demographic variables. For the service-related variables, the study has found that the variables of water quality (i.e. water taste, color, and smell) were all significant in influencing the level of citizens\u27 satisfaction, where the satisfaction varied according to the incidents of facing problems in the water quality. For the variables investigated under the service quality, the study has found that only water pressure, continuity of water flow during the day, and the water company\u27s response to the service urgent needs were significant in influencing the citizens\u27 satisfaction level, while the other variables of having a functioning water meter, facing problems in water bills, and accessibility to the water service information were not influential in affecting the citizens\u27 level of satisfaction regarding the water public service. For the non service-related variables, the study has found that regarding the socioeconomic characteristics of the citizens, the education level of respondents was significant in affecting their level of satisfaction; while on the contrary, the monthly spending average of the household has not show any significance. The demographic characteristics of the citizens have been investigated, and showed that, the gender, and rural-urban distribution of the citizens were significant in affecting the level of satisfaction regarding the water service, yet, the citizens\u27 age failed to show a significant influence. The findings of the study highlight the importance of improving the service-related factors, in order for the water companies to increase the level of citizens\u27 satisfaction with the service

Nematodes associated with soybean (Glycine max) in upper Egypt

Dix-sept espèces de nématodes phytoparasites ont été récoltées dans les champs de soja des Gouvernorats de Menia, Assiut et Sohag, en Haute Egypte. Les espèces #Helicotylenchus pseudorobustus, Longidorus pisi, Pratylenchoides ritteri, P. variabilis, rotylenchulus parvus et #Tylenchorhynchus annulatus sont signalées pour la première fois en Egypte. #Merlinius brevidens est rencontré avec une fréquence relativement élevée tandis que #Pratylenchus zeae est présent en populations assez denses. #Meloidogyne javanica, M. incognita, Pratylenchus zeae, H. pseudorobustus, R. parvus et #Xiphinema sp. pourraient également avoir une grande importance dans les champs de soja de Haute Egypte. Les populations de #Meloidogyne javanica et #M. incognita sont plus élevées dans les sols sableux que dans les sols sablo-argileux ou argileux. #Pratylenchus zeae et #M. brevidens sont présents en populations élevées dans les trois types de sol, et plus particulièrement dans les sols sableux. Les populations de #H. pseudorobustus sont relativement élevées dans les sols argileux, tandis que pour #R. parvus les sols sablo-argileux sont plus favorables. (Résumé d'auteur

Spectral studies of some hydroxy-derivatives of anthraquinones

The u.v., visible, and i.r. spectra of several hydroxy-anthraquinones are discussed and the bands are assigned. These bands are compared with those of anthracene and anthraquinone. The band at 207 nm. is assigned to a n-sigma* transition; the bands at 252, 272, and 326 nm. are assigned by measuring spectra in solvents of various polarities. The stability constant for the 12-dihydroxyanthraquinone-ethanol complex is obtained

Impact of ridge–furrow water harvesting system on faba bean (Vicia faba L.) production under rainfed conditions in Matrouh, Egypt

AbstractIn the North Western Coastal Zone (NWCZ) of Egypt, low rainfall results in poor crop production. Different techniques should be examined to enhance the crop yield productivity and increase the water use efficiency. The ridge–furrow water harvesting system (RFWHS) is examined under the rainfed conditions in the NWCZ of Egypt over the two growing seasons of 2012/2013 and 2013/2014. Two ridge:furrow ratios of 120:60 and 60:60cm ridge:furrow were used and compared to the conventional cultivation in a flat plot. The RFWHS was combined with different plant densities produced from three different row spacing (i.e., 20, 30, 60cm). The faba bean yield was highly influenced by the ridge:furrow ratio, the seed yield was increased by 47% and 128.2% when the 60:60cm ridge:furrow ratio was used as compared to the conventional cultivation in the first and second seasons, respectively. The row spacing of 30cm apart produced the highest seed yield of 491.1kg/ha in the first season and 261.3kg/ha in the second season as compared to 20cm and 60cm row spacing. The water use efficiency followed the same pattern as that of seed yield; it was the highest for the 60:60cm ridge:furrow ratio and the highest for the 30cm row spacing. It is concluded that the RFWHS can be used effectively in increasing faba bean production and maximizing water use efficiency in limited rainfall areas

Comparison of measured and calculated consolidation settlements of thick underconsolidated clay

AbstractThis study investigates the consolidation settlement of thick deep deposit of underconsolidated clay encountered east of Port Said in Egypt. The foundation soil of the studied area includes a 35m thick deposit of very soft to medium stiff silty clay. Calculated settlements for a container terminal constructed in this area are compared with two years of field measurements. Consolidation parameters were defined for this site from laboratory and cone penetration tests (CPT). Upper and lower bounds of calculated settlements were calculated using one-dimensional consolidation theory for the range of working container loads. Settlement monitoring was conducted using settlement plates at eight (8) locations. Field measured settlements were compared to calculated settlements to validate the soil properties and evaluate the rationality of the calculated settlements. Field measured settlements fell within the upper and lower bounds of the calculated settlements. The results of this study confirmed that the deep clay deposit is underconsolidated, which poses a geotechnical challenge to potential construction in this area due to expected excessive settlements. In addition, the study showed that applying the one-dimensional consolidation theory using consolidation parameters estimated from CPT and laboratory tests for underconsolidated clays reasonably estimated the magnitude and rate of consolidation settlement