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排序方式: 共有415条查询结果,搜索用时 281 毫秒
11.
12.
Ali Fouad Keith Phalp John Mathenge Kanyaru Sheridan Jeary 《Software Quality Journal》2011,19(2):411-430
Model-Driven Architecture (MDA) brings benefits to software development, among them the potential for connecting software
models with the business domain. This paper focuses on the upstream or Computation-Independent Model (CIM) phase of MDA. Our contention is that, whilst there are many models and notations available
within the CIM phase, those that are currently popular and supported by the Object Management Group (OMG) may not be the most
useful notations for business analysts nor sufficient to fully support software requirements and specification. Therefore,
with specific emphasis on the value of the Business Process Modelling Notation (BPMN) for business analysts, this paper provides
an example of a typical CIM approach before describing an approach that incorporates specific requirements techniques. A framework
extension to MDA is then introduced, which embeds requirements and specification within the CIM, thus further enhancing the
utility of MDA by providing a more complete method for business analysis. 相似文献
13.
In this paper we formulate power systems as nonlinear nearly Hamiltonian systems. Using the invariance principle for ordinary differential equations, necessary and sufficient conditions for asymptotic stability are established and a new method of estimating the domain of attraction of the stable equilibrium point is developed. The present results constitute a novel approach to stability analysis and involve the following three steps:
- Given a system with dissipation, the stability of its equilibrium is ascertained by determining the stability of the associated conservative system.
- Attractivity of the stable equilibrium of the entire system (with dissipation) is determined from the system topology.
- An estimate of the domain of attraction of the asymptotically stable equilibrium is obtained by making use of results obtained in (a) and (b).
14.
S. S. Fouad E. A. A. El-Shazly M. R. Balboul S. A. Fayek M. S. El-Bana 《Journal of Materials Science: Materials in Electronics》2006,17(3):193-198
The optical properties of As30Se70-xSnx with (x = 0, 1, 2 and 3 at Sn %) thin films have been investigated. The films used in these studies were thermally evaporated. The
structural characterization revealed that the as-deposited films were amorphous in nature. The spectral and optical parameters
have been investigated using spectrophotometric measurements of transmittance in the wavelength range (200–1100 nm). The optical
constants were determined from the interference maxima and minima using the Swanepole method. The dispersion of the refractive
index is discussed in terms of the single-oscillator Wemple-Didomenico model. The optical-absorption edge and the optical
band gap are calculated from the absorption coefficient values using the non direct transition model proposed by Tauc’s extrapolation
procedure. The relation between the optical gap and chemical composition in As-Se-Sn glassy system is discussed in terms of
the average heat of atomization Hs and the average coordination number Nc. 相似文献
15.
The sludge production and settleability have been estimated experimentally in a completely mixed biofilm-activated sludge reactor (hybrid reactor). A steady-state hybrid reactor was run at different stages of suspended biomass concentration (X) under constant values of influent substrate concentration (So) and hydraulic retention time (HRT). The values of X were gradually decreased in these stages until the system completely washed out of the suspended biomass and converted to pure biofilm reactor. As a result, the role of biofilm in the treatment gradually increased with an increase in the effluent substrate concentration (S). The experiment was supported by a mathematical expression for describing the sludge yield in the system under the previous conditions. The experimental and theoretical studies in the present work reveal that there is a critical phase of the hybrid system at which the system produces a high rate of excess sludge. That critical phase is found at a specific ratio between the suspended and the attached growth. Avoiding that critical phase enables the sludge production in the hybrid reactor to be reduced and optimized. Further, the minimum sludge production was found when the biofilm is theoretically inactive for chemical oxygen demand (COD) removal (S相似文献
16.
This paper studies the use of multicast together with proxy nodes for reliably disseminating data from a single source to a large number of receivers. In order to achieve reliability, data must be retransmitted in case of loss either by the source or by special network nodes, called proxies. Each proxy is responsible for reliably delivering the data to a subgroup it is assigned. The multicast tree is partitioned into subgroups that form a hierarchy rooted at the source, hence the term hierarchical reliable multicast. The performance of this approach strongly depends on the topology and the loss characteristics of the underlying tree and the location of proxies. In the first part of the paper, we study the processing and bandwidth performance of such a reliable multicast dissemination given the tree and the placement of proxies. In the second part of the paper, we develop dynamic programming algorithms that give a placement of a fixed number of proxies on an arbitrary tree that minimizes the bandwidth used for reliable transfer. The first algorithm provides an optimal solution to the multicast proxies location problem in polynomial time, in the number of nodes and proxies. The second is an approximation algorithm that gives a solution with cost within a chosen precision from the optimal, in an improved running time. An optimal and an approximate solution are also provided for the proxies location problem if unicast is used for transmissions. Applications of this dynamic programming approach to related problems are discussed. 相似文献
17.
Fouad Boukli HacèneMiloud Tahar Abbés Nachida Kasbadji MerzoukLarbi Loukarfi Hacene Mahmoudi Matheus F.A. Goosen 《Renewable & Sustainable Energy Reviews》2012,16(1):29-36
A mathematical simulation model was developed that can determine the three-dimensional wind velocity field over a complex terrain. The Ténès area in the Valley of Cheliff in Algeria was used as a case study. This region is exposed to south-west circulation that makes it favorable to the use of wind energy. Knowledge of wind fields is crucial for predicting the dispersion of pollutants, for forecasting meteorological weather, for fire spread prediction and in the design and implementation of wind turbines. By means of a mass consistent model, an in-house program was developed to calculate the three-dimensional wind velocity field in the study region. The model was supported by a numerical box in which flow through is allowed for in the upper and lateral boundaries. The bottom boundary through which no flow through occurs was determined by the topographic relief at the surface. From measured wind velocities, observed values were calculated by interpolation-extrapolation. Using an optimization method, the adjusted velocities were obtained from constraints, observed velocities and the continuity equation. The model was verified with wind point data, the relative error did not exceed 6%. 相似文献
18.
Fatma A. Morsy Samya El-Sherbiny Marwa Samir Osama A. Fouad 《Journal of Coatings Technology and Research》2016,13(2):307-316
Nano-TiO2 pigments in pure crystallographic anatase and rutile phases have been successfully prepared by hydrothermal at 120°C and hydrolysis methods, respectively. The laboratory-prepared pigments were characterized parallel to two commercial pigments of the same crystal structure. All pigments were applied in paper coating mixtures, and their influence on coated paper properties was systematically investigated. X-ray diffraction investigation showed that the laboratory-prepared pigments using the hydrothermal method at 120°C were pure anatase, whereas hydrolysis method produced pure rutile phase pigment. The application of the prepared nanopigments and the corresponding commercial TiO2 phases in paper coating revealed that clay/rutile nano-TiO2 pigments in paper coating mixture decreased coated paper roughness more than blending clay with anatase nano-TiO2 pigments. Commercial nano-TiO2 pigments increased porosity of coated paper at both the 30% and 50% addition of nano-TiO2 pigments to clay, while laboratory-prepared nano-TiO2 pigments highly decreased it at 30% addition of nano-TiO2 to clay, compared to clay only. Blending of clay/nano-TiO2 pigments improved both brightness and opacity of the coated paper where commercial pigments are more effective. Burst, tensile strength, stretching, and TEA were improved in the case of all pigments. The 50% addition of the prepared and commercial nanopigments in conjunction with clay improved the mechanical coated paper properties more than 30% addition (except the cases of stretching and TEA of the commercial pigments). The coated paper samples were offset printed. It was found that blending of clay/nano-TiO2 pigments improved print density. Commercial nano-TiO2 pigments improved print gloss more than the laboratory-prepared ones. This result was found consistent with the results of coated paper roughness. 相似文献
19.
Meriem Yatim Rahal El Kahkahi Taoufik El-Askri Samia El Oirdi Fouad Benhnini Adnane El Yaacoubi Abdelmounaim Mouhajir Ali Amechrouq Abdelilah Rahou Majida Hafidi Rachid Zouhair 《Journal of the American Oil Chemists' Society》2022,99(8):685-696
Morphological characterization was investigated by agro-morphological criteria related to carob seed size in four different moroccan regions collected in 2018 and 2019. There was no significant difference (p ≤ 0.05) on the seeds lengths and widths. However, a significant difference between seeds thickness and total seeds weight per pod (p ≤ 0.05) were observed between these four populations. The fatty acid, sterol, tocopherol, hydrocarbon, and the unoxygenated composition of carob seed extracts (Ceratonia siliqua L.) were studied. The mean fat yield of the seeds obtained is 1.53%–2.17%, 2.14%–2.15%, 1.61%–1.62%, 1.71%–1.75% for, respectively, the P1 (Meknes), P2 (Fez), P3 (Khemisset), and P4 (Marrakech) in 2018 and 2019. The seed oil was extracted with hexane and the analysis of the fatty fraction was performed by gas chromatography–mass spectrometry (GC–MS). Results show that the major fatty acids for 2018 and 2019 are linoleic acid (61.48%–61.52%, 52.12%–52.14%, 57.76%–58.15%, 61.33%–61.52%), palmitic acid (15.78%–15.81%, 16.44%–16.45%, 19.11%–18.37%, 20.24%–20.32%), oleic acid (11.03%–11.04%, 8.72%–8.82%, 8.51%–8.61%, 8.41%–8.53%), stearic acid (4.35%–3.14%, 5.40%–5.43%, 3.12%–3.13%, 0.96%–1.56%), and cerotic acid (0.62%–0.53%, 4.51%–4.52%, 4.03%–4.06%, 3.84%–3.87%). The unsaturated fatty acids (69.39% in 2018 and 69.68% in 2019) are the most dominant in the four seed extracts compared to the saturated fatty acids. In addition, the oil carob seeds analysis revealed the presence of γ-tocopherol, α-tocopherol and four sterols that included campesterol, stigmasterol, and β-sitosterol. Moreover, the determination of hydrocarbon and un-oxygenated compounds confirmed the existence of major compounds such as heptadecane, 2-methyltriacontane, 1-iodo hexadecane and 1-iodo octadecane. The hierarchical analysis based on the morphological and chromatographic characterization of the seeds allowed the identification of three groups. Consequently, the first group consisted of populations from Marrakesh (P4) and Khemisset (P3), the second group consisted of the P1 from Meknes, and the P2 from Fez constituted the third group. 相似文献
20.
Medjahed Sidali Kheloufi Abdelkrim Bobocioiu Ema Kefaifi Aissa Kerkar Fouad Lebbou Kheirreddine 《SILICON》2022,14(1):87-97
Silicon - In this work the reverse flotation as beneficiation process for high-purity silica valorization from Draissa quartz deposits (Algeria) is studied as a potential raw material for... 相似文献