Stiffness matrix structural analysis

Computer program for stiffness of structure with lumped masses, weightless members, and many degrees of freedom - structural dynamic

The development of surface morphology during ion etching

This thesis investigates the changes in surface shape which Occur when solid surfaces are subjected to bombardment and erosion by Energetic ion beams. The aspects which are studied lay particular emphasis on the type of problems encountered in the electronics industry where ion etching is used for the production of micro-relief on many commercial devices. Ion etching is also used extensively in surface analysis using techniques such as Auger Electron Spectroscopy, X-ray Photoelectron Spectroscopy and Secondary Ion Mass Spectroscopy both for surface cleaning and composition-depth profiling. [Continues.

Structural Analysis and Matrix Interpetive System /SAMIS/ program Technical report, Feb. - Aug. 1966

Development of characteristic equations and error analysis for computer programs contained in structural analysis and matrix interpretive syste

Coupled structural/thermal/electromagnetic analysis/tailoring of graded composite structures

Accomplishments are described for the first year effort of a 5-year program to develop a methodology for coupled structural/thermal/electromagnetic analysis/tailoring of graded composite structures. These accomplishments include: (1) the results of the selective literature survey; (2) 8-, 16-, and 20-noded isoparametric plate and shell elements; (3) large deformation structural analysis; (4) eigenanalysis; (5) anisotropic heat transfer analysis; and (6) anisotropic electromagnetic analysis

Group implicit concurrent algorithms in nonlinear structural dynamics

During the 70's and 80's, considerable effort was devoted to developing efficient and reliable time stepping procedures for transient structural analysis. Mathematically, the equations governing this type of problems are generally stiff, i.e., they exhibit a wide spectrum in the linear range. The algorithms best suited to this type of applications are those which accurately integrate the low frequency content of the response without necessitating the resolution of the high frequency modes. This means that the algorithms must be unconditionally stable, which in turn rules out explicit integration. The most exciting possibility in the algorithms development area in recent years has been the advent of parallel computers with multiprocessing capabilities. So, this work is mainly concerned with the development of parallel algorithms in the area of structural dynamics. A primary objective is to devise unconditionally stable and accurate time stepping procedures which lend themselves to an efficient implementation in concurrent machines. Some features of the new computer architecture are summarized. A brief survey of current efforts in the area is presented. A new class of concurrent procedures, or Group Implicit algorithms is introduced and analyzed. The numerical simulation shows that GI algorithms hold considerable promise for application in coarse grain as well as medium grain parallel computers

Integrated modeling and parallel computation of laser-induced axisymmetric rod growth

To fully investigate a pyrolytic Laser-induced chemical vapor deposition (LCVD) system for growing an axisymmetric rod, a novel integrated three-dimensional mathematical model was developed not only to describe the heat transport in the deposit and substrate, but also to simulate the gas-phase in the heated reaction zone and its effect on growth rate. The integrated model consists of three components: the substrate, rod, and gas-phase domains. Each component is a separate model and the three components are dynamically integrated into one model for simulating the iterative and complex process of rod deposition. The gas-phase reaction is modeled by the gas-phase component, an adaptive domain attached on the top part of the rod. Its size and mesh decomposition is dynamically determined by the rod temperature distribution and the chosen threshold. The temperature and molar ratio are predicted and used to adjust the growth rate, by taking into account the diffusion limited growth regime, and to improve the simulation of entire deposition process. The substrate component describes the heat flow into the substrate, and the substrate surface temperature can be used to predict the initial rod growth which may affect the successive growth of the rod. The rod growth process is simulated using a layer-by-layer axisymmetric model. For each layer, the rod grows along the outward normal direction at each point on the rod surface. This simplified model makes the process more predictable and easier to control by specifying the height of the rod and the number of total iterations. Finite difference schemes, iterative numerical methods, and parallel algorithms were developed for solving the model. The numerical computation is stable, convergent, and efficient. The model and numerical methods are implemented sequentially and in parallel using a standard C++ code and Message Passing Interface (MPI). The program can be easily installed and executed on different platforms, such as Unix and Windows XP. Computation in the gas-phase domain is encapsulated in a C++ class, and it is convenient for users to choose either the integrated or the kinetic model to perform simulation of rod growth. Parallel implementation improves the computational performance. To demonstrate the capability of the integrated model, silane is chosen as the precursor to grow the axisymmetric rod with silicon as deposit and graphite as substrate. The integrated 3D LCVD model and the corresponding numerical methods are applied to simulate the gas-phase reaction process, and to predict heat transfer, molar ratio, initial and successive rod growths and growth time at each iteration. It is found that the diffusion-limited growth can affect the deposition process and must be taken into account when the temperature is higher than a certain threshold. The initial rod growth can affect the successive rod growth and its geometry. This modeling approach may provide a useful means for investigating the effect of different model parameters for optimizing the LCVD process

Автоматична система визначення координат БПЛА у багатопозиційних комплексах звукового моніторингу

Робота публікується згідно наказу ректора від 29.12.2020 р. №580/од "Про розміщення кваліфікаційних робіт вищої освіти в репозиторії НАУ"The purpose of the work is to develop an automatic detection system for unmanned aerial vehicles on the basis of sound information The paper deals with sensors methods and algorithms for increasing the accuracy of UAV coordinate detection based on the modified Newton method. The Newton method was studied with the aim of reducing the time of calculating coordinates. It is established that in order to obtain sufficient accuracy of coordinate detection, the Jacobi matrix must be calculated on the first three steps of the iteration. A study of parametric sensitivity of the difference-range-finding method was conducted and it was established that the relative error in detecting the arrival delay time of the signal should be within 5%, only then correct identification of the coordinates may be possible. In addition, an extremal statement of the problem of the difference-distance-finding method was investigated on the basis of the quadratic function minimization method, which allows taking into account the relative error ofdetermining the delay time of arrival of a signal on each of the stations separately by introducing a weight coefficient. The emergence of unmanned aerial vehicles with less noisy engines significantly reduced the quality of their detection and signal processing, forcing developers to look for new ways and means to increase the accuracy of detection and impedance of individual vehicles and air defense groups. In turn, passive means of sound monitoring have a significant advantage over active means, consisting mainly of the hidden work of their work. However, the exact characteristics of determining the coordinates of passive systems of the sacred location are considerably inferior to similar characteristics of the active systems. In view of the rather high errors (10% and above) of UAV coordinates measurements, the problem of increasing the accuracy of their operation remains relevant for passive sound monitoring systems

Solitons in nonlinear lattices

This article offers a comprehensive survey of results obtained for solitons and complex nonlinear wave patterns supported by purely nonlinear lattices (NLs), which represent a spatially periodic modulation of the local strength and sign of the nonlinearity, and their combinations with linear lattices. A majority of the results obtained, thus far, in this field and reviewed in this article are theoretical. Nevertheless, relevant experimental settings are surveyed too, with emphasis on perspectives for implementation of the theoretical predictions in the experiment. Physical systems discussed in the review belong to the realms of nonlinear optics (including artificial optical media, such as photonic crystals, and plasmonics) and Bose-Einstein condensation (BEC). The solitons are considered in one, two, and three dimensions (1D, 2D, and 3D). Basic properties of the solitons presented in the review are their existence, stability, and mobility. Although the field is still far from completion, general conclusions can be drawn. In particular, a novel fundamental property of 1D solitons, which does not occur in the absence of NLs, is a finite threshold value of the soliton norm, necessary for their existence. In multidimensional settings, the stability of solitons supported by the spatial modulation of the nonlinearity is a truly challenging problem, for the theoretical and experimental studies alike. In both the 1D and 2D cases, the mechanism which creates solitons in NLs is principally different from its counterpart in linear lattices, as the solitons are created directly, rather than bifurcating from Bloch modes of linear lattices.Comment: 169 pages, 35 figures, a comprehensive survey of results on solitons in purely nonlinear and mixed lattices, to appear in Reviews of Modern Physic

The stimulation of emissions in the whistler mode

Imperial Users onl