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Propagation and Energy Transfer
Published in James D. Taylor, Introduction to Ultra-Wideband Radar Systems, 2020
Robert Roussel-Dupré, Terence W. Barrett
This chapter examines in some detail the key issues associated with the propagation of an electromagnetic wave through the Earth’s atmosphere. In order to appreciate the limitations and approximations inherent to existing treatments of radio wave propagation in the Earth’s atmosphere, it is necessary first to understand how electromagnetic waves interact with matter. The description of wave propagation in terms of the effects of the medium on the incident phase front and wave number forms the basis for the development of geometrical optics. The resulting analysis is applicable primarily to propagation through the Earth’s ionosphere at altitudes above 70 km where the plasma density is sufficiently high and scale lengths are sufficiently long to significantly affect the electromagnetic pulse. The physical processes inherent to the propagation of an electromagnetic wave through the Earth’s atmosphere depend strongly on the frequency content of the wave and on its power level.
Signals Properties
Published in Samir I. Abood, Digital Signal Processing, 2020
Let us now substitute the exponential sequence x(n) = zn. Here z is a complex number, which may be expressed in the usual complex number forms wherever that becomes useful in the analysis. Let us assume that the response is of the form y(n) = H(z)zn. Substitution into the difference equation then produces 1+a1z−1+a2z−2+⋯+apz−pH(z)=b0+b1z−1+⋯+bqz−q
Near-Wall Full Reynolds Stress Closure in Complex Internal Flow Configurations: Numerical Implementation, 2D and 3D Turbomachinery Applications
Published in Chunill Hah, Turbomachinery Fluid Dynamics and Heat Transfer, 2017
Near-wall turbulence models have made significant inroads into applied CFD environments in the past decade. A hierarchy has developed for these models, whose common feature is extended validity to regions where the local turbulence Reynolds number is low. Near-wall algebraic eddy viscosity models enjoy persistent popularity today, due to their computational efficiency and (for some applications) ease of implementation, but suffer the limitations of prescribed mixing length models. Transport near-wall closures (two-equation and Reynolds stress) were introduced nearly simultaneously with their more popular high Reynolds number forms in the mid-1970s but remained impractical for 3D flows until the mid-1980s. In the two-equation model class, the last decade has seen a clear transition away from high Reynolds number forms, both in the literature and in industrial application environments. This transition has been engendered by vigorous and ongoing modelling research and significant increases in digital computer capability. Numerous groups have also been actively pursuing near-wall full Reynolds stress modelling since the first published model of this type was put forward in the 1970s.
Augmented Reality Application Selection Framework Using Spherical Fuzzy COPRAS Multi Criteria Decision Making
Published in Cogent Engineering, 2022
Criteria are defined as C1 (Hardware Support), C2 (Content Support), C3 (Authoring), C4 (Tracking), C5 (Registration), C6 (Integration & Real-time data), C7 (Interaction & Collaboration), C8 (Architecture & Deployment) and C9 (Cost/Affordability). The last criterion C9 is also considered as benefit criteria and users are asked to evaluate not the cost of the product but its affordability. Highly affordable alternatives (easier payment terms, cheaper maintenance and license costs, etc.) will be ranked higher. Each DMs judgements of criteria and alternative are listed in Tables 5, 7 and 9 respectively. The linguistic terms are converted to SF number forms using Table 3. The SF number equivalent of the judgements are displayed in Table 6, for DM1, Table 8 for DM2 and Table 10 for DM3. Based on experience, age, or other factors, different weights can be assigned to DMs. To demonstrate different weighting for DMs, the normalized weights are generated and displayed in Table 4 using Equation 6.
Comparing the development of the multiplication of fractions in Turkish and American textbooks
Published in International Journal of Mathematical Education in Science and Technology, 2018
Tuğrul Kar, Gürsel Güler, Ceylan Şen, Ercan Özdemir
After modelling this activity, EM explained creating area models of the (fraction)x(fraction) and (fraction)x(wholenumber) forms. In addition, EM supported the use of words that were appropriate to the structure of the operation presented. In this context, EM avoided the word ‘times’ to refer to multiplying fractions for the following reasons: Verbal cues are generally an inadequate guide in deciding which number model to use in solving a problem. For example, ‘more’ does not necessarily signal ‘add.’ But ‘many of’ and ‘part of’ do seem to be closely tied to multiplication. A student is more likely to succeed when responding to as ‘one-half of 12,’ rather than as ‘one-half times 12’. (Bell et al., [74], p. 616)
On the resistance and speed loss of full type ships in a seaway
Published in Ship Technology Research, 2019
Shukui Liu, Baoguo Shang, Apostolos Papanikolaou
The B2/LPP versus LPP of the selected ships has been plotted in Figure 2 against the IHS-Fairplay database (2011). It is observed that the selected ships cover the whole range of the tanker fleet, thus they represent typical designs of the current world fleet. Figure 3 shows the investigated speeds of each ship, in both dimensional and non-dimensional (Froude number) forms, plotted as a function of ship length and DWT, respectively.