139 research outputs found
Single parameter scaling in 1-D localized absorbing systems
Numerical study of the scaling of transmission fluctuations in the 1-D
localization problem in the presence of absorption is carried out. Violations
of single parameter scaling for lossy systems are found and explained on the
basis of a new criterion for different types of scaling behavior derived by
Deych et al [Phys. Rev. Lett., {\bf 84}, 2678 (2000)].Comment: 7 pages, 6 figures, RevTex, submitted to Phys. Rev.
Reduction of a fan vibration activity in a life support system of oil and gas stations
Relevance. Electromechanical fans are widely used in life support systems of oil and gas stations, operate in conditions of vibration, high rotational speeds and loads. Design, technological and operational reasons influence vibration activity of an electromechanical device. The greatest "contribution" to the existing vibrations, according to the frequency spectrum, is made by the imperfection of the design elements of the ball bearing. They are: separator movement, variable stiffness under the action of radial load, interaction of micro-dimensions of working surfaces, facet and waviness of working surfaces of rings and balls. In addition, the resulting vibrations negatively affect both the reliability and durability of the fan. Since it is technically impossible to completely eliminate the vibration activity of an electromechanical device, it is advisable to reduce it with the help of a technical solution by introducing a damping element into a kinematic circuit of the vibration source. In this regard, the development of a damping device is an integral technical task that helps to reduce the vibration activity of technical life support systems of oil and gas stations, as well as to improve the quality of environmental conditions of human life. To reduce vibration activity, a damper design is proposed that takes into account various types of energy dissipation. However, given the dense spectrum of vibration frequencies from ball bearings, a viscous friction element is introduced into the damper design. To determine the effectiveness of reducing vibration activity, a model of the damper in question was made based on the developed 3D model. For tests in determining the effectiveness of applying a viscous friction element, two variants of the damper design were used. In the first version of the damper design, there was no viscous friction element, and in the second version there was one. According to the test results of the damper layouts, it can be seen that the developed technical solution to reduce the vibration activity of the electromechanical device has practical confirmation. The studies underlying the developed design of the damper with a viscous friction element allows for reduction in the vibration amplitude. Object. Electromechanical device in operating mode. Aim. To describe the vibration activity in the operating mode of an electromechanical device in the entire spectrum of disturbing effects acting along the axes, taking into account the imperfect geometry of ball bearing parts; to develop a damper for reducing the vibration activity level in the electromechanical device. Methods. Vibration diagnostics, computational mathematics, measuring instruments, software "Vibration recorder-F", "Vibration Recorder-M2", "Logger"-recorder and "Bearing". Results. The paper demonstrated the effectiveness of the proposed technical solution to reduce the vibration amplitude in the operating frequency range of the electromechanical device rotor up to 4 times compared with the corresponding maximum amplitude value without its use
Solid-state damper for reducing vibration activity of an electromechanical device of a life support system of oil and gas stations
Relevance. Mechanical vibrations are a common and technically important process that has a negative acoustic effect on human health and in some cases is a harmful production factor. In devices, the presence of vibration is caused by exciting influences of various physical nature: mechanical, electromagnetic, aerodynamic. The reason for their occurrence are defects in parts and assemblies, the technical principle of the ball bearing device, as well as the coincidence of the operating frequency of the device with natural frequency of the structural elements. Since it is technically impossible to completely eliminate the vibration activity of an electromechanical device, the actual topic of scientific research is the technical task of developing a damping device with determining its effectiveness to reduce the vibration activity of an electromechanical device, thereby minimizing the effects of concomitant harmful production factors on humans. To study this problem, a 3D model of the construction of a solid-state damper based on aluminum foam has been developed, according to which two layouts are made with different depths of cylindrical ducts used to install screws. The results of measuring vibration characteristics showed that the material used as a vibration dampener has damping properties and can be used to reduce the level of vibration activity of an electromechanical device. A comparison of the test results of the solid-state damper layouts showed that using layout No. 1 reduces the vibration amplitude up to 3 times compared with layout No. 2. Object. Fragment of the damping element of the vibration damper of a solid-state damper based on aluminum foam. Aim. To develop a design for a solid-state damper based on aluminum foam and determine the effectiveness of its use to reduce the level of vibration activity of an electromechanical device of the life support system of oil and gas stations. Methods. Modern approaches of vibration diagnostics, computational mathematics and measuring instruments. Results. There is a possibility of creating a solid-state damper based on aluminum foam to solve the problems of reducing the amplitude of vibration in the operating frequency range of the rotor of an electromechanical device compared with the corresponding vibration characteristics without damping elements
Belagash: A Newly Discovered Kipchak-Era Site in Central Kazakhstan
Introduction. Despite the long history of archaeological research in Central Kazakhstan, many aspects of culture inherent to its medieval nomadic population remain understudied. So, the ninety-year-long excavations of eighth-to-twelfth century sites have shaped certain ideas about the latter primarily on the basis of statuary objects and thirteen sanctuary-type facilities with varying structural patterns. Funeral rites can be traced only in one attributed burial discovered in cultural layers of the Bronze Age settlement of Kent. Goals. The study attempts a complete historical summary of investigations into eighth-to-twelfth century sites across Central Kazakhstan, and introduces into scientific circulation some newly discovered material from the site of Belagash. Materials and methods. All the studied objects of Belagash are rather similar graveside structures in the form of unsodded stone mounds sized 2–3 to 13 m. Unfortunately, facilities nos. 1–3 were looted and have yielded only scarce finds that provide insufficient data for any reconstruction of rituals. And since such graveside structures can to some extent be traced in both Early Iron Age and medieval monuments, the question of their dating shall be left open for the time being. Results. Facility no. 4 is of utmost interest. Its formal typological features attest to it may cluster with eighth/ninth-to-eleventh century sites. It was containing some scattered horse remains accompanied by an iron stirrup, a buckle, a bronze belt tip, and an appliqué plaque. Typological characteristics of the stirrup are crucial to identifying the historical period in question: analogues from the Irtysh River valley and the Altai may date the investigated site to the eighth/ninth throughout eleventh centuries CE. Conclusions. It is urgent to emphasize the significance of the material from Belagash since the latter does add to the meager data on the culture of Central Kazakhstan’s population at the final stage of the Early Middle Ages
Observation of a node in the quantum oscillations induced by microwave radiation
The microwave induced magnetoresistance in GaAs/AlGaAs heterostructure was
studied at temperatures below 1K and frequencies in the range of 150-400 GHz. A
distinct node in the Shubnikov- de Haas oscillations, induced by the microwave
radiation, is clearly observed. The node position coincides with the position
of the cyclotron resonance on the carriers with effective mass (0.068 +/-
0.005) m0.Comment: to be published in Solid State Communication
Swarmodroid 1.0: A Modular Bristle-Bot Platform for Robotic Active Matter Studies
Large swarms of extremely simple robots (i.e., capable just of basic motion
activities, like propelling forward or self-rotating) are widely applied to
study collective task performance based on self-organization or local
algorithms instead of sophisticated programming and global swarm coordination.
Moreover, they represent a versatile yet affordable platform for experimental
studies in physics, particularly in active matter - non-equilibrium assemblies
of particles converting their energy to a directed motion. However, a large set
of robotics platforms is being used in different studies, while the universal
design is still lacking. Despite such platforms possess advantages in certain
application scenarios, their large number sufficiently limits further
development of results in the field, as advancing some study requires to buy or
manually produce the corresponding robots. To address this issue, we develop an
open-source Swarmodroid 1.0 platform based on bristle-bots with reconfigurable
3D-printed bodies, external control of motion velocity, and basic capabilities
of velocity profile programming. In addition, we introduce AMPy software
package in Python featuring OpenCV-based extraction of robotic swarm kinematics
accompanied by the evaluation of key physical quantities describing the
collective dynamics. We perform a detailed analysis of individual Swarmodroids'
motion characteristics and address their use cases with two examples: a cargo
transport performed by self-rotating robots and a velocity-dependent jam
formation in a bottleneck by self-propelling robots. Finally, we provide a
comparison of existing centimeter-scale robotic platforms, a review of key
quantities describing collective dynamics of many-particle systems, and a
comprehensive outlook considering potential applications as well as further
directions for fundamental studies and Swarmodroid 1.0 platform development.Comment: 18 pages, 7 figures, 1 table + Supplementary Information. Comments
are welcom
Secoisolariciresinol Diglucoside of Flaxseed and Its Metabolites: Biosynthesis and Potential for Nutraceuticals
Secoisolariciresinol diglucoside (SDG), found mainly in flaxseed, is one of the essential lignans. SDG, as well as the beneficial fatty acid composition and high fiber content, has made flaxseed an important source of functional food or nutraceutical ingredients. Various studies have shown that SDG offers several health benefits, including protective effects against cardiovascular diseases, diabetes, cancer, and mental stress. These health benefits have been attributed to the antioxidant properties of SDG. Additionally, SDG metabolites, namely mammalian lignans, enterodiol and enterolactone, have shown promising effects against cancer. Therefore, understanding the biosynthetic pathway of SDG and its molecular mechanisms is a key to enable the production of new flaxseed cultivars rich in nutraceutical content. The present review highlights studies on the different health benefits of SDG, as well as lignan biosynthesis in flaxseed and genes involved in the biosynthetic pathway. Since SDG, the predominant lignan in flaxseed, is a glycosylated lignan, we also focus on studies investigating the genes involved in secoisolariciresinol glycosylation. These genes can be used to produce new cultivars with a novel level of glycosylation or lignan composition to maximize the yields of lignans with a therapeutic or protective potential
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