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排序方式: 共有658条查询结果,搜索用时 15 毫秒
41.
Roula Khadra Juan Antonio Sagardoy Suzan Taha Nicola Lamaddalena 《Water Resources Management》2017,31(13):4227-4238
A major shortcoming of Participatory Irrigation Management and Irrigation Management Transfer (PIM/IMT) is the absence of Monitoring & Evaluation (M&E) systems that accompany these processes and become a major instrument to correct, improve and learn. Although at the global level some countries have exerted efforts to implement M&E systems, these still present limitations, as the review of the international experiences shows. The Mediterranean situation is even more dramatic since only Tunisia implements an M&E system, whereas Egypt has shyly moved in this direction with a limited practical application. This state of affairs led the authors to develop a set of guiding principles to develop an M&E system to be applied in countries where PIM/IMT is adopted. This paper revises the main international efforts devoted to assess the performance of PIM/IMT and the state of the art of these processes in Southern and Eastern Mediterranean Countries. Moreover, it sets the framework and analyses the main sustaining factors for the development of a new M&E system for these countries. 相似文献
42.
Ahmad A Hamza Taha ZN Sokkar Kermal A El‐Farahaty Mohammed I Raslan 《Polymer International》2010,59(7):1021-1030
A creep device attached to an automated multiple‐beam Fizeau system in transmission was modified with a designed digital ruler. This device allows on‐line measurements of fibre length during creep experiments in terms of an analogue voltage value. The influence of sustained stress values on creep deformation and optical properties (n||, n? and Δn) for polypropylene (PP) fibres was studied interferometrically. The opto‐viscoelastic properties of PP fibres were determined for three different values of constant applied stress of 11.536, 18.717 and 25.905 MPa, at room temperature. Also, the variations of the cross‐sectional area and Poisson's ratio were studied during creep extensions. The compliance curves were obtained as a function of both time and applied stresses. Empirical formulae are suggested to describe the creep compliance curves for PP fibres, and the constants of these formulae were determined and described at each applied stress. A Kelvin chain was used to model the mechanical behaviour of the PP fibres under study. The effect of strain on the mean refractive indices, orientation function density and crystallinity was investigated as a result of the recorded data. Microinterferograms are given for illustration. The modified creep device with the designed digital ruler enables one to obtain instantaneous automatic accurate recording of fibre length values during creep experiments. Calculation of refractive indices, orientation function and crystallinity shows a difference in material behaviour at small stresses from that at higher stresses which may be attributed to different strain rates caused by different stresses. Copyright © 2010 Society of Chemical Industry 相似文献
43.
Interest in finding exact solitary wave solutions of nonlinear evolution equations by means of different methods has grown steadily in recent years. These exact solutions are important to understand the mechanism of the complicated nonlinear physical phenomena. By use of the Jacobi elliptic function method, we find the exact analytic solitary wave solutions for the RKL model with cubic-quintic non-Kerr terms, describing the propagation of extremely short pulses in optical fibers. These new solutions may be useful for describing the propagation of optical pulses in non-Kerr media. 相似文献
44.
A heat transfer model of a parallelepiped tank, full of water and covered with translucent insulation of diffuse material to solar energy, is developed considering the multiple absorptions and reflections to evaluate the heat gain or loss by water. The effect of the optical properties and thickness of insulation on that heat gained or lost by water is investigated. The results of a comparative study show that translucent insulation is more effective than opaque insulation and no insulation as far as the energy gained by water is concerned for outdoor solar storage tanks. 相似文献
45.
Bazil Taha?AhmedEmail author Miguel Calvo?Ramón Leandro?De?Haro Ariet 《Wireless Personal Communications》2004,31(1-2):19-31
The uplink capacity and the interference statistics (mean and variance) of the sectors of the cigar-shaped W-CDMA microcell are studied. A model with eighteen sectors is used to analyze the uplink. The microcells are assumed to exist in a long tunnel with at least nine base stations. The hybrid model of propagation is used in the calculations. The capacity and the interference statistics of the sectors are studied in terms of the most important parameters: sector radius, specific attenuation factor, antenna sidelobe levels, bend losses and the power control standard deviation error. 相似文献
46.
Comparison of spectral fluorescent signatures-based models to characterize DOM in treated water samples 总被引:1,自引:0,他引:1
Statistical procedures enable a multivariate analysis of the measurements to identify specific characteristics of the dissolved organic matter (DOM) fractions in raw natural water, including the concentrations. In this work, three already established models were used to predict the concentrations of fractions of DOM from spectral fluorescent signatures (SFSs): a general linear regression (GLR), loadings and scores of a principal components analysis (PCA), and a partial least squares regression (PLS). Details about the method undertaken to prepare the fractions were given. Water samples from surface water treatment plants in New Jersey were used for the testing. In all cases, PLS have shown much better biases and accuracies than GLR and PCA models. Hydrophilic neutral, however, showed poor performances (bias 33%) due to the isolation technique used. Recommendations were provided in order to improve the DOM characterization through SFS, which linked to PLS make a powerful and cost-effective surrogate parameter to characterize DOM. 相似文献
47.
Ahmad F. Taha Ahmed Elmahdi Jitesh H. Panchal Dengfeng Sun 《International journal of control》2013,86(5):920-934
The insertion of communication networks in the feedback loops of control systems is a defining feature of modern control systems. These systems are often subject to unknown inputs in a form of disturbances, perturbations, or attacks. The objective of this paper is to design and analyse an observer for networked dynamical systems with unknown inputs. The network effect can be viewed as either a perturbation or time-delay to the exchanged signals. In this paper, we (1) review an unknown input observer (UIO) design for a non-networked system, (2) derive the networked unknown input observer (NetUIO) dynamics, (3) design a NetUIO such that the effect of higher delay order terms are nullified and (4) establish stability-guaranteeing bounds on the networked-induced time-delay and perturbation. The formulation and results derived in this paper can be generalised to scenarios and applications where the signals are perturbed due to a different source of perturbation or delay. 相似文献
48.
49.
The multidimensional multiple-choice knapsack problem (MMKP) is an extension of the 0–1 knapsack problem. The core concept has been used to design efficient algorithms for the knapsack problem but the core has not been developed for the MMKP so far. In this paper, we develop an approximate core for the MMKP and utilize it to solve the problem exactly. 相似文献
50.
Riad Taha Al-Kasasbeh 《Advances in Engineering Software》2011,42(8):547-554
Methods for the selection of candidates for operators of man-machine systems are analyzed. Vector mean estimates of group intelligence and estimates defining the group’s collective decision-making ability to obtain the unified solution to the selection problem and to retain the correct original solution to the problem, and estimates of solution quality and interoperability in correct decision-making are proposed. The properties of the suggested estimates are studied with a test example of five candidates. Amongst these properties are estimates of the group’s psychological traits, such as average estimates of professional competence, static components of the intelligence vector for tested candidates, components of the trainability vector for tested candidates, average intelligence estimates for tested candidates, average estimates for the basis of groups, average different-mindedness estimates of groups, variations in the trainability of operators, and arithmetic estimates of group intelligence variability such as levels of awareness, knowledge level, mean speed of knowledge variation, comprehension and motivation in operators’ reasoning. 相似文献