Nutation damping of dynamically tuned gyroscopes

The paper deals with the problem of nutation damping of dynamically tuned gyroscopes (DTG). Unlike the common two-axis gyroscopes, the DTG damping torques caused by dry and viscous frictions are absent in gimbal bearings, while those due to the rotor/gaseous medium interaction are insufficient to provide the required nutation damping. A physical explanation is given to the damping torques induced in the gyroscope by the magnetoelectric torque detectors. Control coils of the latter are included in the output circuits of the electronic amplifiers. The equation is proposed for the calculation of the damping torque. The numerical estimate of the damping coefficient is given in this paper

Design and analysis of power supply and information transfer to three-axis gyroscope stabilizer platform

The paper focuses on problems of the engineering implementation of 3-axis gyrostabilizer of the camera for orthophotography performed from light and ultralight aircrafts. The functional diagram of gyrostabilizer is characterized by a lighter ball-bearing having a large inner diameter used for the platform suspension on its internal (vertical) axis. The problem is to transfer the supply voltage to the platform and the electric signals to and from the platform. Design solutions concerning the power supply and information transfer are supported by the experimental techniques suggested in this paper, namely: the use of the rolling contact; three-phase gyro motor power supply replaced by that from the single-phase network; signal transmission from the precession angle sensor using the air transformer; current and voltage frequency division; DC mode selection for the torquer. The results obtained prove the efficiency of the suggested design solutions

Nutation damping of dynamically tuned gyroscopes

The paper deals with the problem of nutation damping of dynamically tuned gyroscopes (DTG). Unlike the common two-axis gyroscopes, the DTG damping torques caused by dry and viscous frictions are absent in gimbal bearings, while those due to the rotor/gaseous medium interaction are insufficient to provide the required nutation damping. A physical explanation is given to the damping torques induced in the gyroscope by the magnetoelectric torque detectors. Control coils of the latter are included in the output circuits of the electronic amplifiers. The equation is proposed for the calculation of the damping torque. The numerical estimate of the damping coefficient is given in this paper

Design and analysis of power supply and information transfer to three-axis gyroscope stabilizer platform

The paper focuses on problems of the engineering implementation of 3-axis gyrostabilizer of the camera for orthophotography performed from light and ultralight aircrafts. The functional diagram of gyrostabilizer is characterized by a lighter ball-bearing having a large inner diameter used for the platform suspension on its internal (vertical) axis. The problem is to transfer the supply voltage to the platform and the electric signals to and from the platform. Design solutions concerning the power supply and information transfer are supported by the experimental techniques suggested in this paper, namely: the use of the rolling contact; three-phase gyro motor power supply replaced by that from the single-phase network; signal transmission from the precession angle sensor using the air transformer; current and voltage frequency division; DC mode selection for the torquer. The results obtained prove the efficiency of the suggested design solutions

Synthesis, molecular docking analysis and in vitro evaluation of new heterocyclic hybrids of 4-aza-podophyllotoxin as potent cytotoxic agents

International audienceTwo different synthetic approaches to novel heterocyclic hybrid compounds of 4-azapodophyllotoxin were investigated. The obtained products were characterized by infrared spectroscopy, nuclear magnetic resonance spectroscopy, and high-resolution mass spectrometry. MTT protocol was then performed to examine the cytotoxic activity of these products against KB, HepG2, A549, MCF7, and Hek-293 cell lines. The cytotoxic assessment indicated that all products displayed moderate to high cytotoxicity against all tested cancer cell lines. The most active compound 13k containing the 2-methoxypyridin-4-yl group exhibited selective cytotoxicity against KB, A549, and HepG2 cell lines with the IC50 values ranging from 0.23 to 0.27 mu M, which were between 5- to 10-fold more potent than the positive control ellipticine. Compounds 13a (HetAr = thiophen-3-yl) and 13d (HetAr = 5-bromofuran-2-yl) displayed high cytotoxic selectivity for A549 and HepG2 cancer cell lines when compared to the other cancer cell lines and low toxicity to the normal Hek-293 cell line. Molecular docking study was conducted to evaluate the interaction of new synthesized compounds with the colchicine-binding-site of tubulin. Besides that, physicochemical and pharmacokinetic properties of the most active compounds 13h,k were predicted

Moral Economy and the Upper Peasant: The Dynamics of Land Privatization in the Mekong Delta

This paper examines how people mobilize around notions of distributive justice, or ‘moral economies’, to make claims to resources, using the process of post‐socialist land privatization in the Mekong Delta region of southern Vietnam as a case study. First, I argue that the region\u27s history of settlement, production, and political struggle helped to entrench certain normative beliefs around landownership, most notably in its population of semi‐commercial upper peasants. I then detail the ways in which these upper peasants mobilized around notions of distributive justice to successfully press demands for land restitution in the late 1980s, drawing on Vietnamese newspapers and other sources to construct case studies of local land conflicts. Finally, I argue that the successful mobilization of the upper peasants around such a moral economy has helped, over the past two decades, to facilitate the re‐emergence of agrarian capitalism in the Mekong Delta, in contrast to other regions in Vietnam