ALGORITHM FOR CONTROLLING THE SPECTRUM OF EIGENFREQUENCIES AND VIBRATION MODES BY CHARDING THE GEOMETRIC PARAMETERS OF MAST SESTEMS

The article considers a model of a mast with six levels of fastening of cables. The main attention in the work is considered to the methods of control of the natural frequency spectrum, due to the use of methods of sensitivity analysis and optimization. The above task is achieved by varying the cross-sectional area of the pipes - racks. Automation of computational processes is provided by programming the built-in module in the Revit program. For more convenient and faster control of the natural frequency spectrum, the algorithm described above was written in a free add-on for Revit - Dynamo. With the help of so-called nodes, an application was created that took data from the depicted 3D model Revit and performed calculations. This allows you to easily use optimality conditions similar to the maximum principle. The sensitivity analysis for the first and second own is carried out in the work. The mechanism of their management within the limits of the investigated model is shown. The relations in the case of the problem of finding the natural frequency extremum with a given number are given, provided that the total amount of varied bands is fixed. The numerical control algorithm is based on the necessary optimality conditions in the form of the maximum principle for rod models. A variant of varying the area of the belts along the height of the mast is proposed. The sensitivity analysis for the first and second natural frequencies is carried out and its use for construction of effective computational process is shown. Based on the results of the work, a working software algorithm was created for fast analysis of mast oscillations on extensions. Graphs of zones of possible change of the first and second frequencies are resulted. The distribution of the cross-sectional area for frequencies is shown. To compare the results of natural frequency calculations on other calculation models, the first and second natural frequencies of bending oscillations were calculated by the finite element method in the SCAD complex. The errors for the points of the curves (constant in the height of the mast area of the belts) do not exceed 10%. It should be noted that the consideration of optimization problems of the above type on the basis of finite element models is quite difficult; for them it is not possible to formulate the necessary conditions of optimality similar to the principle of maximum.

Dynamic loading of friction disks in automotive transmissions

The article describes a refined method for design studies of friction disks that are integrated into automotive transmissions. A technique is presented to enable finding the natural frequency spectrum exhibited by disks as distributed mass multicomponent bodies. Grounds are given that explicate the necessity to evaluate the stability of oscillations when high-frequency dynamic processes evolve in a nonlinear system after friction clutches are disengaged and when friction clutches are being engaged and wavelike plastic deformations emerge giving rise to overheated spots. The article also sheds light on specific features inherent in the off-design behavior subsequent to the stopping of the clutch booster and pressure unbalance in the clutch booster plenums. The research studies have produced a number of technical solutions that reduce the amplitude of the high-frequency oscillations, which are generated after friction clutches are disengaged and result in plastic deformations of mating surfaces as well as disturbed axial movability of friction disks. They have substantiated the necessity that the relevant linear velocity should be restricted having determined the boundaries of tolerated linear velocities of revolving friction disks. The article presents results of researching into the processes consequent to pressure unbalance in the friction clutch booster plenums and proposes technical solutions to do away with its adverse effects.

New Challenges Implementing Cognitive Radio in Wireless Sensor Networks: A Survey

With the growing demand of wireless applications, radio spectrum has become a scare resource. Cognitive Radio (CR) technology has been considered as an important solution to optimize the utilization of natural frequency spectrum. Numerous researches are performed on deploying CR in cellular networks. In this paper, we introduced new challenges on integration of CR technology and Wireless Sensor Networks (WSN), and some potential solutions are proposed.