Mechanisms Of Fracturing In Structures Built From Topologically Interlocked Blocks

Failure of materials is in many cases associated with initiation and subsequent propagation of macroscopic fractures. Consequently, in order to increase the strength, one needs to inhibit either crack initiation or propagation. The principle of topological interlocking provides a unique opportunity to construct materials and structures in which both routes of the strength increase can be realised. Materials and structures built on the basis of this principle consist of many elements which are hold together by the special geometry of their shape, together with an external constrain. The absence of the binder phase between the elements allows the interfaces to arrest macroscopic crack propagation. In addition, with sufficiently small size of the elements an increase in local strength and, possibly, in the stress for crack initiation can be achieved by capitalising on the size effect. Furthermore, the ability of some interlocking structures to tolerate missing elements can serve to prevent the avalanche-type failure initiated by failure of one of the elements. In this paper, experimental results and a theoretical analysis with regard to this possibility are presented

Modeling antenna system with support-rotating device based of stewart platform

Проаналізовано конструкцію, імітаційну модель опорно-поворотного пристрою антенної системи на основі кінематичної платформи Стюарта як альтернативного варіанта класичним азимутально-кутомісним підвіскам. Проаналізовано особливості керування таким механізмом, наведено результати моделювання руху лінійних приводів для наведення антени та супроводу космічних апаратів.The paper considers the design, simulation model support-rotation device antenna system based on kinematic Stewart platform as an alternative classic azimuth – elevation platform. The features of this control mechanism, given the results of modeling the movement of linear actuators for antenna pointing and tracking of satellite

Investigate of dynamic errors of precision system antenna control with asynchronous driver

Досліджено динамічні похибки, що виникають при наведенні та супроводі траєкторій супутників у системі керування великогабаритною антеною з частотно регульованим асинхронним електроприводом при використанні різних законів керування. Наведено результати моделювання та зроблено порівняння з експериментальними даними, отриманими при випробуваннях розробленої системи керування антеною під час відпрацювання тестових траєкторій.This paper considers the investigation of dynamic errors occurring in the control system of precision antenna complex using frequency regulated asynchronous electric drive as the actuator. Simulation model of the system induction motor - frequency regulator is synthesized. The detailed parameters calculation of asynchronous motors (AM) and frequency regulator is carried out. Simulation model of frequency speed AM adjusting for precision control of AS mechanical modules in the system Matlab/Simulink is synthesized. PID controller coefficients is synthesized for the model of frequency regulation as a part of the overall as management system to control the trajectory support. Computing power UFR appreciates the current angular position of the rotor flux linkage vector-based interpretation in real-time systems of differential equations, according to the mathematical model of the asynchronous engine. The comparative results of the survey errors obtained using simulation modeling in different modes for different law of the torque support at low revs are presented. The experimental data of operation of the large-sized antenna control system with vector control in frequency regulated device during working of test trajectories are presented. The results of simulation and comparison are made on experimental data obtained while testing AS «EgyptSat-1» during working out the test trajectories. The developed technique makes possible to choose reasonably the method of control and parameters of the system asynchronous motor – the device of frequency regulation in the problems of control systems synthesis by complex objects. The use of techniques for creation precision control systems for antenna complexes to ensure communication with LEO satellites of remote sensing and the radio systems is of practical value, which will improve reliability and reduce the cost of such systems

Accelerator system for the PRISM based muon to electron conversion experiment

The next generation of lepton flavor violation experiments need high intensity and high quality muon beams. Production of such beams requires sending a short, high intensity proton pulse to the pion production target, capturing pions and collecting the resulting muons in the large acceptance transport system. The substantial increase of beam quality can be obtained by applying the RF phase rotation on the muon beam in the dedicated FFAG ring, which was proposed for the PRISM project.This allows to reduce the momentum spread of the beam and to purify from the unwanted components like pions or secondary protons. A PRISM Task Force is addressing the accelerator and detector issues that need to be solved in order to realize the PRISM experiment. The parameters of the required proton beam, the principles of the PRISM experiment and the baseline FFAG design are introduced. The spectrum of alternative designs for the PRISM FFAG ring are shown. Progress on ring main systems like injection and RF are presented. The current status of the study and its future directions are discussed.Comment: Studies performed within the PRISM Task Force initiativ