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排序方式: 共有246条查询结果,搜索用时 15 毫秒
1.
G. S. Ghali 《Water Resources Management》1989,3(1):35-47
The mathematical model which was developed in part I of this work for multi-dimensional analysis of soil moisture in irrigated fields is converted into computer algorithms. The algorithms are capable of emulating many field conditions of practical applications during both design and operation phases. The model is subjected to various tests, the results of which are reported here. The tests in various modes of simulations verified the numerical performance of the model and the accuracy of its predictions. The model provides a powerful tool for detailed studies of soil moisture dynamics in one or multi-dimensional problems irrigated fields 相似文献
2.
M. Bounoughaz E. Salhi K. Benzine E. Ghali F. Dalard 《Journal of Materials Science》2003,38(6):1139-1145
Zinc is used in the oil industry as a sacrificial anode for protecting steel storage tanks from corrosion. The behaviour of a sample of zinc from the Algerian metallurgy industry (zinc A) and a commercially available zinc (zinc B) was compared in an electrolyte from storage tank drainage water. The corrosion potential measurements for zinc A confirmed that this material could be used as a sacrificial anode. The polarization curves of the two materials (zinc A and zinc B) were different, zinc A being the least polarized. Thus, the same corrosion protection could be obtained with a lower surface ratio (S
Zn/S
Fe) for Zinc A. Cyclic voltammetry curves provided evidence of a surface layer formed by dissolution products. To provide protection over extended periods of time, the zinc anode must be oversized. The two types of zinc tested were comparable.The results of the impedance spectroscopy study confirmed the previous results. The corrosion layer formed on zinc A was not prejudicial to dissolution. Hence, the properties of this zinc were found to be satisfactory for its use as a sacrificial anode. 相似文献
3.
The galvanostatic technique on a laboratory scale has been shown to be a useful tool in detecting the presence of nodules on the cathode during copper electrodeposition by using the value of the starting electrolytic potential and by the presence of a cathodic polarization peak on the potential–time curve. Studying the morphology of the deposit with a scanning electron microscope at various magnifications confirmed the galvanostatic results. It is postulated that inappropriate concentrations and/or ratios of the additives (thiourea, gelatin and chloride ions) are associated with a certain current density that generates intergranular microcracks due to adsorption of the additives and leads to the formation of nodules at the macroscale. 相似文献
4.
Chao AC Ziadeh BI Diau GY Wijendran V Sarkadi-Nagy E Hsieh AT Nathanielsz PW Brenna JT 《Lipids》2003,38(4):425-429
One of the major survival challenges of premature birth is production of lung surfactant. The lipid component of surfactant,
dipalmitoyl PC (DPPC), increases in concentration in the period before normal term birth via a net shift in FA composition away from unsaturates. We investigated the influence of dietary DHA and arachidonic acid (AA)
on lung FA composition and DPPC concentration in term and preterm baboons. Pregnant animals/neonates were randomized to one
of four groups: breast-fed (B), term formula-fed (T−), preterm formulafed (P−), and preterm fed formula supplemented with DHA-AA (P+). Breast milk contained 0.68%wt DHA and the P+ group formula contained 0.61%wt DHA. In the preterm groups (P− and P+), pregnant females received a course of antenatal corticosteroids. At the adjusted age of 4 wk, neonate lung tissue was harvested,
and FA composition and DPPC were analyzed. Palmitate was ∼28%wt of lung total FA and no significant differences were found
among the four treatment groups. In contrast, DPPC in the B group lung tissue was significantly greater than DPPC in the unsupplemented
groups, but not compared with the P+ group. The B and P+ groups were not significantly different in DHA and AA, but were different compared with the unsupplemented (T, P−) groups. These results indicate that LCP supplementation increases lung DHA and AA, without compromising overall lung 16∶0
or DPPC. The shift in FA composition toward greater unsaturation in the groups consuming LCP supported improved surfactant
lipid concentration in preterm neonate lungs. 相似文献
5.
Nowadays, tandem structures have become a valuable competitor to conventional silicon solar cells, especially for perovskite over silicon, as metal halides surpassed Si with tunable bandgaps, high absorption coefficient, low deposition, and preparation costs. This led to a remarkable enhancement in the overall efficiency of the whole cell and its characteristics. Consequently, this expands the usage of photovoltaic technology in various fields of applications not only under conventional light source spectrum in outdoor areas, i.e., AM1.5G, but also under artificial light sources found indoors with broadband intensity values, such as Internet of things (IoTs) applications to name a few. We introduce a numerical model to analyze perovskite/Si tandem cells (PSSTCs) using both crystalline silicon (c-Si) and hydrogenated amorphous silicon (a-Si:H) experimentally validated as base cells. All proposed layers have been studied with J-V characteristics and energy band diagrams under AM1.5G by using SCAPS-1D software version 3.7.7. Thereupon, the proposed architectures were tested under various artificial lighting spectra. The proposed structures of Li4Ti5O12/CsPbCl3/MAPbBr3/CH3NH3PbI3/Si recorded a maximum power conversion efficiency (PCE) of 25.25% for c-Si and 17.02% for a-Si:H, with nearly 7% enhancement concerning the Si bare cell in both cases. 相似文献
6.
In this paper, we present a new sufficient condition for absolute stability of Lure system with two additive time-varying delay components. This criterion is expressed as a set of linear matrix inequalities (LMIs), which can be readily tested by using standard numerical software. We use this new criterion to stabilize a class of nonlinear time-delay systems. Some numerical examples are given to illustrate the applicability of the results using standard numerical software. 相似文献
7.
In this paper, we present a new sufficient condition for absolute stability of Lure system with two additive time-varying
delay components. This criterion is expressed as a set of linear matrix inequalities (LMIs), which can be readily tested by
using standard numerical software. We use this new criterion to stabilize a class of nonlinear time-delay systems. Some numerical
examples are given to illustrate the applicability of the results using standard numerical software. 相似文献
8.
Sherif Ghali 《The Visual computer》2009,25(4):367-375
Computer graphics is ostensibly based on projective geometry. The graphics pipeline—the sequence of functions applied to 3D
geometric primitives to determine a 2D image—is described in the graphics literature as taking the primitives from Euclidean
to projective space, and then back to Euclidean space.
This is a weak foundation for computer graphics. An instructor is at a loss: one day entering the classroom and invoking the
established and venerable theory of projective geometry while asserting that projective spaces are not separable, and then
entering the classroom the following week to tell the students that the standard graphics pipeline performs clipping not in
Euclidean, but in projective space—precisely the operation (deciding sidedness, which depends on separability) that was deemed
nonsensical.
But there is no need to present Blinn and Newell’s algorithm (Comput. Graph. 12, 245–251, 1978; Commun. ACM 17, 32–42, 1974)—the crucial clipping step in the graphics pipeline and, perhaps, the most original knowledge a student learns in a fourth-year
computer graphics class—as a clever trick that just works. Jorge Stolfi described in 1991 oriented projective geometry. By declaring the two vectors
and
distinct, Blinn and Newell were already unknowingly working in oriented projective space. This paper presents the graphics
pipeline on this stronger foundation.
相似文献
Sherif GhaliEmail: |
9.
Résumé L'électrodissolution de sulfure de plomb obtenu par fusion ou par frittage, a été étudiée dans l'acide sulfamique par les méthodes cyclovoltammétrique, potentiocinétique et potentiostatique. Les paramètres examinés sont: la température, la vitesse de rotation de l'électrode, l'oxygène, le pH et la concentration de l'acide. L'identification par voie chimique, l'analyse par rayonsX et l'observation par la microscopie électronique à balayage ont permis de définir les produits de la polarisation anodique. Le comportement anodique de PbS en milieu sulfamique a été discuté et précisé davantage.
The electrodissolution of lead sulphide, prepared by fusion or by sintering in sulphamic acid, was studied by cyclic voltammetric, potentiodynamic and potentiostatic methods. The parameters examined were: temperature, rotation speed of the electrode, oxygen concentration, pH and the acid concentration. The chemical identification,X-ray analysis and scanning electron microscope observations permitted the definition of the anodic polarization products. The anodic behaviour of PbS in sulphamic medium was critically discussed and is explained in more detail.相似文献
10.
Saylor David M. Fridy Joseph El-Dasher Bassem S. Jung Kee-Young Rollett Anthony D. 《Metallurgical and Materials Transactions A》2004,35(7):1969-1979
Techniques are described that have been used to create a statistically representative three-dimensional model microstructure
for input into computer simulations using the geometric and crystallographic observations from two orthogonal sections through
an aluminum polycrystal. Orientation maps collected on the observation planes are used to characterize the sizes, shapes,
and orientations of grains. Using a voxel-based tessellation technique, a microstructure is generated with grains whose size
and shape are constructed to conform to those measured experimentally. Orientations are then overlaid on the grain structure
such that distribution of grain orientations and the nearest-neighbor relationships, specified by the distribution of relative
misorientations across grain boundaries, match the experimentally measured distributions. The techniques are applicable to
polycrystalline materials with sufficiently compact grain shapes and can also be used to controllably generate a wide variety
of hypothetical microstructures for initial states in computer simulations.
This article is based on a presentation made at the symposium “Characterization and Representation of Material Microstructures
in 3-D” held October 8–10, 2002, in Columbus, OH, under the auspices of ASM International’s Phase Transformations committee. 相似文献