Conditions of exact tracking by the linear system output of the standard model of a reduced order

A problem is considered for an exact tracking by the output of a linear stationary system presented in the space of states of the standard model of a reduced order in comparison with the dimension of the system state vector. A minimum possible order of the standard model is defined, at which it is possible to perform the exact tracking of it by the output, conditions are defined of the exact tracking by the output of the standard model of a reduced order, and also a set of the control laws that ensure the exact tracking and the internal stability of the system. The solution relies on the method of canonization of matrices. A methodical example is given.     

Robust control of composite beams

The structure uncertainty effect is considered on actively controllable composite beam that is a part of the structure of a civil building in a seismodangerous zone. The solution of the problem for active control of vibrations of the composite beam is based on the introduction of a simplified model of sensors and an actuator, which are implemented in the form of piezoelectric plates pasted on two opposite planes of the beam. A suggestion is made of the practical approach that affords the robust control of the composite beam and is founded on the modern H ₂- and H _∞-methods of the theory of control. The effectiveness of the suggested approach for the suppression of vibrations of the composite beam under consideration is illustrated by the examples of numerical modeling.     

Problems of boundary observability of elastic vibrations described by the system of telegrapher equations

Problems are solved for the observability of elastic vibrations described by various boundary problems for the system of telegrapher equations. The initial conditions that generate observable vibrations are found in the explicit form. The necessary time period of an observation is defined. The solutions of observation problems are given in the case of the classical and generalized solutions of the class L ₂ of appropriate boundary problems.     

Total cross section of solid mesitylene, toluene and a mixture of them at thermal neutron energies

The total neutron cross sections of mesitylene, toluene and a solution 3:2 by volume of mesitylene and toluene were measured at the electron LINAC based pulsed neutron source of Centro Atómico Bariloche. Measurements were performed at 180 K, 120 K and 31.6 K for mesitylene and at 120 K and 31.6 K for toluene and a solution 3:2 by volume of mesitylene and toluene. The systems are potential moderator materials to be considered in the design of a cold neutron source due to their high resistance to radiation and the richness in low-energy excitations of their frequency spectra, that lead to produce an enhanced cold neutron flux.     

New measurement and evaluation of the excitation function of Ni(p,n) reaction for the production of Cu

One of the radioisotopes for which a growing interest exists in nuclear medicine is ⁶⁴Cu. Its branched decay makes it suitable for both diagnostic and therapeutic purposes. Activation cross sections of the proton induced reaction on enriched ⁶⁴Ni have been studied using the stacked foil technique up to 24 MeV. The experimental cross sections are compared with values available from literature. Thick target yields, based on the discrete measured values of the cross sections are calculated and allow a better estimation of the optimum production parameters.     

Methods of intelligent diagnosis for control of flexible moving craft

A new approach to the control of moving flexible mechanical systems based on the methods of intelligent diagnosis and forecast was proposed. While observing the requirements on stability and performance of control of the main (“rigid”) craft motion, this approach also stabilizes its elastic oscillations. A notion of the “model” function of the effect of basic control on the elastic oscillations in the presence of the dominating mode was introduced. The loop for adaptive adjustment of the basic algorithm of power-optimal control of the flexible craft motion was designed. For the proposed method of control of the elastic multifrequency moving craft such as the large space structure, some results of modeling were presented.     

Using the method of phase biplane to study dynamics of interactions of the elastic structural oscillations of the flexible spacecraft with the control system

A modal-physical representation of the mathematical model of flexible spacecraft enabling one to specify a diversity of the distinctions of the dynamics of controllable motion of the flexible objects was determined. The method of phase biplane enabling strict analysis of the dynamics of relay control of orientation of a flexible object with one dominating mode was described and extended to the method of the fuzzy phase biplane for approximate study of the dynamics of the multifrequency flexible spacecraft. Consideration was given to some important questions concerning the impact of structural flexibility on stability and performance of the control system of orientation of flexible spacecraft.     

Measurement of cross-sections for the (p, xn) reactions in natural molybdenum

Cross-sections for the residual radionuclide productions by proton-induced activation on natural molybdenum were measured up to 40 MeV by using a stacked-foil technique at the MC50 cyclotron of the Korea Institute of Radiological and Medical Sciences (KIRAMS). This work has given a new data set for the formation of the investigated radionuclides. The present results for most of the radionuclides showed in general good agreement with the earlier reported data as well as the theoretical data taken from the calculations based on the ALICE-IPPE code. The integral yields for thick targets were also deduced from the measured cross-sections of the produced radionuclides. The optimum production of the ^99mTc radionuclide with minimum impurities can be obtained at the energy ranges from 10 to 23 MeV, where the production yields were obtained as 597.15 MBqμA⁻¹h⁻¹ at saturation. The measured cross-sections are used for production of medically important radionuclides such as ^99mTc, ^94mTc and ^93m,gTc by using the medium-energy cyclotrons.     

Monte Carlo simulation of the Greek Research Reactor neutron irradiation facilities

A Monte Carlo simulation of the Greek Research Reactor was carried out using MCNP-4C2 code and continuous energy cross-section data from ENDF/B-VI library. A detailed model of the reactor core was employed including standard and control fuel assemblies, reflectors and irradiation devices. The model predicted neutron flux distributions within the core in good agreement with calculations performed using the deterministic code CITATION and measurements using activation foils. The model is used for the prediction of the neutron field characteristics at the reactor irradiation devices and enables the design and evaluation of experiments involving material irradiations.     

Sharing of secondary electrons by in-lens and out-lens detector in low-voltage scanning electron microscope equipped with immersion lens

To understand secondary electron (SE) image formation with in-lens and out-lens detector in low-voltage scanning electron microscopy (LV-SEM), we have evaluated SE signals of an in-lens and an out-lens detector in LV-SEM. From the energy distribution spectra of SEs with various boosting voltages of the immersion lens system, we revealed that the electrostatic field of the immersion lens mainly collects electrons with energy lower than 40 eV, acting as a low-pass filter. This effect is also observed as a contrast change in LV-SEM images taken by in-lens and out-lens detectors.