Hypersonic flight vehicle trajectory optimization using pattern search algorithm

In this work, trajectory optimization of an aerodynamically controlled hypersonic boost glide class of flight vehicle is presented. In order to meet the mission constraints such as controllability, skin temperature, and terminal conditions etc., the trajectory is optimized using a pattern search algorithm with the lift to drag (L/D) ratio as a control parameter. It is brought out that the approach offers a viable tool for optimizing trajectories for the considered class of vehicles. Further, the effects of the constraints on trajectory shape and performance are studied and the analysis is used to bring out an optimal vehicle configuration at the initial stage of the design process itself. The research also reveals that the pattern search algorithm offers superior performance in comparison with the genetic algorithm for this class of optimization problem.     

Solution of large dense complex matrix equations using a fastFourier transform (FFT)-based wavelet-like methodology

Wavelet-like transformations have been used in the past to compress dense large matrices into a sparse system. However, they generally are implemented through a finite impulse response filter realized through the formulation of Daubechies (1992). A method is proposed to use a very high order filter (namely an ideal one) and use the computationally efficient fast Fourier transform (FFT) to carry out the multiresolution analysis. The goal here is to reduce the redundancy in the system and also guarantee that the wavelet coefficients drop off much faster. Hence, the efficiency of the new procedure becomes clear for very high order filters. The advantage of the FFT-based procedure utilizing ideal filters is that it can be computationally efficient and for very large matrices may yield a sparse matrix. However, this is achieved, as well known in the literature, at the expense of robustness, which may lead to a larger reconstruction error due to the presence of the Gibb's phenomenon. Numerical examples are presented to illustrate the efficiency of this procedure as conjectured in the literature     

Multicast Network Security with Asymmetric Cooperative Relaying

International Journal of Wireless Information Networks - This paper exhibits the confidentiality performance study of a cooperative multicast network consisting of $${\mathcal {K}}$$ asymmetric...     

Fracture characteristics of a burst tested maraging steel rocket motor case

A 0.3 m diameter, 2 m long and 0.0015 m thick, 18 nickel 1800 MNm^–2 grade maraging steel motor case was designed, fabricated and burst tested to gain experience for using the steel as booster case material in satellite launch vehicles. The bursting occurred at 15.2 MPa for which the effective hoop stress worked out to be 1754 MNm^–2 almost equal to the ultimate tensile strength (1764 MNm^–2) of the material in the solution treated and aged condition. The failure analysis revealed that the material failed due to normal tensile overload fracture. The burst test data was used to arrive at fracture mechanics parameters like crack size, gross section area stress and the stress for leak before bursting.     

Periodically Fully Developed Heat and Fluid Flow Characteristics in a Furrowed Wavy Channel

Periodically fully developed two-dimensional (2D) flow in a furrowed wavy channel is investigated numerically at various Reynolds numbers (100–2123). For the laminar and transitional flow regime, the study is done for six geometrically different channels; corresponding to various nondimensional amplitude (0.05, 0.075, and 0.1) and wavelength (0.5 and 1). Critical Reynolds number—for the onset of periodic flow—decreases with increasing amplitude and wavelength. A flow regime map—demarcating steady and unsteady flow regime—is proposed. It is shown that the size of the vortex in streamlines and waviness in isotherms increase with increasing Reynolds number, amplitude and wavelength. The performance of wavy as compared to straight channel is studied with the help of ratio of Nusselt number, friction factor and area-goodness factor, and thermal-performance factor. With increasing Reynolds number, all these parameters remain almost constant in the steady regime and increase almost linearly in the unsteady regime. For the largest Reynolds number (close to 2000) studied here, the increase in the Nusselt number ratio—within the periodic flow regime—is 11.21% and 133% for the amplitude equal to 0.075 and 0.1, respectively, at a wavelength of 0.5; at a wavelength of 1.0, the increase is 101%, 134%, and 181% for the amplitude of 0.05, 0.075, and 0.1, respectively.     

Combination of Ag Substrate Decoration with Introduction of?BaZrO3 Nano-Inclusions for?Enhancing Critical Current Density of?YBa2Cu3O7 Films

The combination of two methods: Ag substrate decoration and introduction of BZO nano-inclusions has been used in a pulsed laser deposition (PLD) method to increase the critical density (J _c ) of YBCO films. The films were deposited on single crystal SrTiO₃ (STO) substrates decorated with various architecture of Ag nano-dots. We have studied the diameter and density of Ag nano-dots and their influence on J _c of BZO-added YBCO films. We found that 15 laser pulses on the Ag target gives an optimum result in increasing J _c in comparison with BZO-doped YBCO films of the same thickness in self-field and low applied magnetic fields. A higher number of laser pulses on the Ag target led to increasing critical current density in high applied magnetic fields only (above 2 T). We have studied films of the thickness from 0.4 ??m to 3.8 ??m and found that the highest J _c at all applied fields investigated is achieved for a 1.2 ??m thick film. The transmission electron microscopy clearly shows BZO nano-rods that provide strong c-axis pinning centres in the films.     

Time-domain measurements with the Hewlett-Packard network analyzerHP 8510 using the matrix pencil method

The generalized pencil of function (GPOF) method, also known as the matrix pencil method, is used to improve the resolution of HP 8510B network analyzer data in the time domain. This method provides for much higher resolution than the Fourier techniques. A comparison of the two methods is given for the example of the Beatty standard. The examples show that a parametric technique such as the GPOF can provide accurate and reliable results with a high degree of resolution even when the fast Fourier transform (FFT)-based technique fails     

Interferometer for use in wave-front testing with a cross slit

A simple and novel interferometric setup for wave-front testing that uses a cross slit is described. In this method, the test beam illuminates a cross slit placed at the front focal plane of a Fourier lens. It selects two orthogonal slices from the test beam, and the interference of these two beams is observed at a slightly defocused plane near the back focal plane. Fringes of different conical forms (circular, elliptical, or hyperbolic) so obtained can be used for testing a coherent wave front in general. The theory, supported by some experimental results, is presented. An application of the method to the study of the nature of asymmetry in the beam profile of a semiconductor diode laser beam is demonstrated.     

Surface topography and hydrogen sensor response of APCVD grown multilayer graphene thin films

Atmospheric pressure chemical vapour deposition was employed to deposit graphene thin films on thermally oxidized p-silicon substrates. Raman spectroscopy and energy dispersive spectroscopy revealed the multilayer nature and the composition of the grown graphene films respectively. The defective nature and the defect density of the graphene films were determined from the Raman experiments. Field effect scanning electron microscopy, transmission electron microscopy and atomic force microscopy were used to study the surface morphology of the multilayer graphene films. The film topography was sensitive to temperature and time of growth. A suitable growth mechanism has been proposed to explain the topographical observations. The large surface area of the multilayer films was found to be suitable for hydrogen sensor applications and the sensing results were correlated with the morphology of the grown films.     

Axial ratio bandwidth improvement of compact planar monopole antenna with dual-band and dual-sense

A small size, dual-band and dual-sense monopole antenna is proposed to improve the axial ratio bandwidth (ARBW). The proposed antenna is considered on a low-cost lossy FR4 substrate with parasitic strips (PSs) and partial ground plane of half guided wavelength dimensions. The dimension of the antenna in terms of wavelength is $\mathbf{0.27}{\mathit{\lambda }}_{\mathbf{0}}\mathit{\times }\mathbf{0.29}{\mathit{\lambda }}_{\mathbf{0}}\mathit{\times }\mathbf{0.02}{\mathit{\lambda }}_{\mathbf{0}}$, where ${\mathit{\lambda }}_{\mathbf{0}}$ is the wavelength at the lowest resonant frequency. The circularly polarized (CP) mode is created for strong orthogonal electric fields ${\mathit{E}}_{\mathit{X}}$ and ${\mathit{E}}_{\mathit{Y}}$. The obtained phase difference (PD) between two electric fields ${\mathit{E}}_{\mathit{X}}$ and ${\mathit{E}}_{\mathit{Y}}$ is varied from ${\mathbf{86}}^{°}$ to ${\mathbf{96}}^{°}$ under ARBW. The achieved ARBW is 3.68–3.8 GHz, 4.84–12.58 GHz, and impedance bandwidth (IBW) is 3.51–3.82 GHz and 4.28–15 GHz. The applications of the proposed antenna are International Telecommunication Union (ITU) for 5G, C-band IEEE 802.11a wireless local area network (WLAN) at 5 GHz (5.15–5.825 GHz) and X-band wireless systems.