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The first two sections in the present chapter are devoted to penetration of shaped-charge (Munroe) jets. Shaped-charge jets are characterized by such tremendous stresses that metal flow can be treated in the framework of potential flow hydrodynamics. Section 13.1 is devoted to the elementary theory of penetration depth of a shapedcharge jet perforating an armor, while Section 13.2 describes a detailed structure of the corresponding metal flow and predicts the crater shape using the hodograph method of complex analysis in the planar case. An estimate for an axisymmetric case is also given in this section. Normal penetration of eroding projectiles into elastic–plastic targets is covered in Section 13.3. The limit of high-speed penetration where pressure and the inertial effects are dominant is considered in Section 13.4, and the quasi-steady regime of penetration of an eroding projectile is treated in Section 13.5. Section 13.6 is devoted to description of normal and oblique penetration of rigid projectiles and comparison with numerous experimental data. Explosion welding discussed in Section 13.7 is also characterized by tremendous stresses, while the resulting metal flow is not only “inviscid” but even compressible. Still, the problem can be reduced to the form appropriate for complex analysis, which reveals some important details of the interface formation between two materials welded by this method. The experimental evidence shows some additional fascinating details which deserve a further analysis.
Shaped-charge Jet Penetration Depth
In 1888, Munroe discovered the phenomenon of so-called shaped-charge (or Munroe) jets. Later on, he described it in the following words (Munroe 1900):
“Among the experiments made … was one upon a safe twenty-nine inches cube, with walls four inches and three quarters thick, made up of plates of iron and steel … When a hollow charge of dynamite nine pounds and a half in weight and untamped was detonated on it, a hole three inches in diameter was blown clear through the wall … The hollow cartridge was made by tying the sticks of dynamite around a tin can, the open mouth of the latter being placed downward.”
A systematic account of the theory and modelling of rotating fluids that highlights the remarkable advances in the area and brings researchers and postgraduate students in atmospheres, oceanography, geophysics, astrophysics and engineering to the frontiers of research. Sufficient mathematical and numerical detail is provided in a variety of geometries such that the analysis and results can be readily reproduced, and many numerical tables are included to enable readers to compare or benchmark their own calculations. Traditionally, there are two disjointed topics in rotating fluids: convective fluid motion driven by buoyancy, discussed by Chandrasekhar (1961), and inertial waves and precession-driven flow, described by Greenspan (1968). Now, for the first time in book form, a unified theory is presented for three topics - thermal convection, inertial waves and precession-driven flow - to demonstrate that these seemingly complicated, and previously disconnected, problems become mathematically simple in the framework of an asymptotic approach that incorporates the essential characteristics of rotating fluids.
Image inpainting methods recover true images from partial noisy observations. Natural images usually have two layers consisting of cartoons and textures. Methods using simultaneous cartoon and texture inpainting are popular in the literature by using two combined tight frames: one (often built from wavelets, curvelets or shearlets) provides sparse representations for cartoons and the other (often built from discrete cosine transforms) offers sparse approximation for textures. Inspired by the recent development on directional tensor product complex tight framelets ($\text{TP}\text{-}\mathbb{C}\text{TF}$s) and their impressive performance for the image denoising problem, we propose an iterative thresholding algorithm using tight frames derived from $\text{TP}\text{-}\mathbb{C}\text{TF}$s for the image inpainting problem. The tight frame $\text{TP}\text{-}\mathbb{C}\text{TF}_{6}$ contains two classes of framelets; one is good for cartoons and the other is good for textures. Therefore, it can handle both the cartoons and the textures well. For the image inpainting problem with additive zero-mean independent and identically distributed Gaussian noise, our proposed algorithm does not require us to tune parameters manually for reasonably good performance. Experimental results show that our proposed algorithm performs comparatively better than several well-known frame systems for the image inpainting problem.
We study a nonpreemptive scheduling on two parallel identical machines with a dedicated loading server and a dedicated unloading server. Each job has to be loaded by the loading server before being processed on one of the machines and unloaded immediately by the unloading server after its processing. The loading and unloading times are both equal to one unit of time. The goal is to minimize the makespan. Since the problem is NP-hard, we apply the classical list scheduling and largest processing time heuristics, and show that they have worst-case ratios, $8/5$ and $6/5$, respectively.
We analyse a parallel (identical) machine scheduling problem with job delivery to a single customer. For this problem, each job needs to be processed on $m$ parallel machines non-pre-emptively and then transported to a customer by one vehicle with a limited physical capacity. The optimization goal is to minimize the makespan, the time at which all the jobs are processed and delivered and the vehicle returns to the machine. We present an approximation algorithm with a tight worst-case performance ratio of $7/3-1/m$ for the general case, $m\geq 3$.
We analyse the coverage performance of cognitive radio networks powered by renewable energy. Particularly, with an energy harvesting module and energy storage module, the primary transmitters (PTs) and the secondary transmitters (STs) are assumed to be able to collect ambient renewables, and store them in batteries for future use. Upon harvesting sufficient energy, the corresponding PTs and STs (denoted by eligible PTs and STs) are then allowed to access the spectrum according to their respective medium access control (MAC) protocols. For the primary network, an Aloha-type MAC protocol is considered, under which the eligible PTs make independent decisions to access the spectrum with probability $\unicode[STIX]{x1D70C}_{p}$. By applying tools from stochastic geometry, we characterize the transmission probability of the STs. Then, with the obtained results of transmission probability, we evaluate the coverage (transmission nonoutage) performance of the overlay CR network powered by renewable energy. Simulations are also provided to validate our analysis.
We provide an elementary method for exploring pricing problems of one spread options within a fractional Wick–Itô–Skorohod integral framework. Its underlying assets come from two different interactive markets that are modelled by two mixed fractional Black–Scholes models with Hurst parameters, $H_{1}\neq H_{2}$, where $1/2\leq H_{i}<1$ for $i=1,2$. Pricing formulae of these options with respect to strike price $K=0$ or $K\neq 0$ are given, and their application to the real market is examined.
A new generalized class of fuzzy implications, called ($h,f,g$)-implications, is introduced and discussed in this paper. The results show that the new fuzzy implications possess some good properties, such as the left neutrality property and the exchange principle.
Rotation plays an essential role in the structure and variation of large-scale flows taking place in the interiors, atmospheres and oceans of planets. Knowledge of common hydrodynamical processes in rotating systems constitutes a major necessary component not only in oceanography, but also in planetary and astrophysical sciences. There have been few systematic accounts of the theory of rotating fluids in the more than quarter of a century since Chandrasekhar (1961) and Greenspan (1968) wrote their classic monographs. The second edition of Greenspan's book, Greenspan (1990), was not a major revision. Other volumes, such as the book edited by Roberts and Soward (1978), while containing some interesting articles, did not present the subject in a unified fashion. More recent books by Vanyo (1993) and Boubnov and Golitsyn (1995) mainly concentrate on experimental studies of general rotating flows. Many important developments have taken place in the study of rotating fluids and it has long been necessary to fill a significant gap in the existing literature.
Over the past several decades the subject of rotating fluids has blossomed remarkably and great strides have been made in our understanding of the topic. Not only have there been very many publications on the classic applications of the theory of rotating fluids to the dynamics of atmosphere and oceans, almost exclusively dealing with thin, nearly two dimensional spherical layers of fluids or infinitely unbounded fluid layers, but also considerable attention has been paid to rotating flows in fluid-filled containers such as cylinders, annuli and thick spherical layers or in complete spheres of fluid. Such studies are often considered to be relevant to the dynamics of planetary and stellar interiors and, more importantly, corresponding laboratory experiments in these fluid-filled rotating containers can be carried out, offering deep insight into the understanding of common processes at the heart of rotating flow phenomena.
It is clearly quite impossible today to cover the theory of rotating fluids to the same degree of completeness as Chandrasekhar (1961) or Greenspan (1968) could for the state of the subject in the 1960s.