573 research outputs found
“I Began Understand Piłsudski, When I Reached His Age”. Memoirs of G.F. Matveev in the Form of Interview
No full textGennady Filippovich Matveev (born in 1943), Doctor of Historical Sciences, Honored Professor of Moscow University, Head of the Department of the History of the Southern and Western Slavs of Moscow State University, one of the leading domestic specialists in the modern history of Poland, tells about his life and professional activities at the request of the editors of the journal Slavic World in the Third Millennium. Born on the banks of the Volga, G.F. Matveev spent his childhood and youth in Western Ukraine. Since 1966, his whole life has been inextricably linked with the Moscow University, where he received a diploma in history, completed his postgraduate studies, defended his candidate's and doctoral theses, and where he has been teaching for half a century and was head of the department for more than three decades. The students of G.F. Matveev completed and defended a large number of diplomas, master's and candidate's theses, they work in different cities of the country and abroad. As a historian, G.F. Matveev invariably relies on deep researches in archives, introduces a lot of new material into circulation, his innovative research on the history of the Soviet-Polish war of 1920 caused fruitful discussions both in Russia and in Poland, prompting other historians to further research. Gennady Filippovich is the author of the first fundamental biography in Russian of the key statesman of Poland of the 20th century Józef Piƚsudski. Not limited to the problems of Polish history, G.F. Matveev turned to comparative historical research on the material of various Slavic countries, in particular, on the ideology of peasant movements in the period between the two world wars. As an author and editor, he took part in the work on textbooks on the history of the southern and western Slavs. For more than half a century, G.F. Matveev maintains close ties with the Institute of Slavic Studies of the Russian Academy of Sciences, he is a member of the editorial boards of historical journals, both Russian and Polish.
G.F. Matveev talks about his post-war childhood, youth, impressions of his student years, about his work at the Moscow University, about his numerous trips to Poland and more than half a century of communication with Polish colleagues. He also shares his opinion on the current development and prospects of Polish studies in Russia, the possibilities for further dialogue between the two cultures
Thermoacoustic Instabilities in the Rijke Tube: Experiments and Modeling
No full textThermoacoustic instability can appear in thermal devices when unsteady heat release is coupled with pressure perturbations. This effect results in excitation of eigen acoustic modes of the system. These instabilities are important in various technical applications, for instance, in rocket motors and thermoacoustic engines.
A Rijke tube, representing a resonator with a mean flow and a concentrated heat source, is a convenient system for studying the fundamental physics of thermoacoustic instabilities. At certain values of the main system parameters, a loud sound is generated through a process similar to that in real-world devices prone to thermoacoustic instability. Rijke devices have been extensively employed for research purposes. The current work is intended to overcome the serious deficiencies of previous investigations with regard to estimating experimental errors and the influence of parameter variation on the results. Also, part of the objective here is to account for temperature field non-uniformity and to interpret nonlinear phenomena. The major goals of this study are to deliver accurate experimental results for the transition to instability and the scope and nature of the excited regimes, and to develop a theory that explains and predicts the effects observed.
An electrically heated, horizontally oriented, Rijke tube is used for the experimental study of transition to instability. The stability boundary is quantified as a function of major system parameters with measured uncertainties for the data collected. Hysteresis in the stability boundary is observed for certain operating regimes of the Rijke tube.
An innovative theory is developed for modeling the Rijke oscillations. First, linear theory, incorporating thermal analysis that accurately determines the properties of the modes responsible for the transition to instability, is used to predict the stability boundary. Then, a nonlinear extension of the theory is derived by introducing a hypothesis for a special form of the nonlinear heat transfer function. This nonlinear modeling is shown to predict the hysteresis phenomenon and the limit cycles observed during the tests.
A new, reduced-order modeling approach for combustion instabilities in systems with vortex shedding is derived using the developed analytical framework. A hypothesis for the vortex detachment criterion is introduced, and a kicked oscillator model is applied to produce nonlinear results characteristic for unstable combustion systems.
The experimental system and the mathematical model, developed in this work for the Rijke tube, are recommended for preliminary design and analysis of real-world thermal devices, where thermoacoustic instability is a concern.</p
Response of Pedunculate Oak (Quercus robur L.) to Adverse Environmental Conditions in Genetic and Dendrochronological Studies
No full textPedunculate oak (Quercus robur L.) is widely distributed across Europe and serves critical ecological, economic, and recreational functions. Investigating its responses to stressors such as drought, extreme temperatures, pests, and pathogens provides valuable insights into its capacity to adapt to climate change. Genetic and dendrochronological studies offer complementary perspectives on this adaptability. Tree-ring analysis (dendrochronology) reveals how Q. robur has historically responded to environmental stressors, linking growth patterns to specific conditions such as drought or temperature extremes. By examining tree-ring width, density, and dynamics, researchers can identify periods of growth suppression or enhancement and predict forest responses to future climatic events. Genetic studies further complement this by uncovering adaptive genetic diversity and inheritance patterns. Identifying genetic markers associated with stress tolerance enables forest managers to prioritize the conservation of populations with higher adaptive potential. These insights can guide reforestation efforts and support the development of climate-resilient oak populations. By integrating genetic and dendrochronological data, researchers gain a holistic understanding of Q. robur’s mechanisms of resilience. This knowledge is vital for adaptive forest management and sustainable planning in the face of environmental challenges, ultimately helping to ensure the long-term viability of oak populations and their ecosystems. The topics covered in this review are very broad. We tried to include the most relevant, important, and significant studies, but focused mainly on the relatively recent Eastern European studies because they include the most of the species’ area. However, although more than 270 published works have been cited in this review, we have, of course, missed some published studies. We apologize in advance to authors of those relevant works that have not been cited
AN INVESTIGATION OF THE ACCURACY OF EMPIRICAL AIRCRAFT DESIGN FOR THE DEVELOPMENT OF AN UNMANNED AERIAL VEHICLE INTENDED FOR LIQUID HYDROGEN FUEL
No full textThesis (Ph.D.), School of Mechanical and Materials Engineering, Washington State UniversityA study was conducted to assess the accuracy of empirical techniques used for the calculation of flight performance for unmanned aerial vehicles. This was achieved by quantifying the error between a mathematical model developed with these techniques and experimental test data taken using an unmanned aircraft. The vehicle utilized for this study was developed at Washington State University for the purpose of flying using power derived from hydrogen stored as a cryogenic liquid. The vehicle has a mass of 32.8 kg loaded and performed a total of 14 flights under battery power for 3.58 total flight hours. Over these flights, the design proved it is capable of sustaining level flight from the power available from a PEM fuel cell propulsion system.The empirical techniques used by the model are explicitly outlined within. These yield several performance metrics that are compared to measurements taken during flight testing. Calculations of required thrust for steady flight over all airspeeds and rates of climb modeled are found to have a mean percent error of 3.2%±7.0% and a mean absolute percent error of 34.6%±5.1%. Comparison of the calculated and measured takeoff distance are made and the calculated thrust required to perform a level turn at a given rate is compared to flight test data. A section of a test flight is analyzed, over which the vehicle proves it can sustain level flight under 875 watts of electrical power. The aircraft's design is presented including the wing and tail, propulsion system, and build technique. The software and equipment used for the collection and analysis of flight data are given. Documentation and validation is provided of a unique test rig for the characterization of propeller performance using a car. The aircraft remains operational to assist with research of alternative energy propulsion systems and novel fuel storage techniques.The results from the comparison of the mathematical model and flight test data can be utilized to assist in the development of similar Unmanned Aerial Vehicles, express the uncertainty in calculated vehicle performance numbers, and assist in identifying error in control system design.School of Mechanical and Materials Engineering, Washington State Universit
Thermoacoustic Phenomena in Small-Scale Systems
No full textThesis (Ph.D.), School of Mechanical and Materials Engineering, Washington State UniversityThermoacoustic phenomena in small-scale systems are investigated, and results are presented on the following topics: the acoustic properties of porous and fibrous materials, the modeling of thermoacoustic resonators with nonuniform medium and boundary conditions, and the harvesting of energy from tonal sound excited by heat addition and vortex shedding.
The transfer function measurement system is used to find the acoustic properties of porous and fibrous materials. The complex wave numbers and characteristic impedances of reticulated vitreous carbon (RVC) and plastic mesh are determined using a variation of the three-microphone and four-microphone methods with the transfer function technique. The wave numbers and characteristic impedances of RVC and plastic mesh can be estimated from the obtained results. To find the effect of temperature difference, relative acoustic power changes across RVC, stacked plastic screens and stacked steel screens atDepartment of Mechanical Engineering, Washington State Universit
Reply to “Discussion of ‘Study of Air-Ventilated Cavity under Model Hull on Water Surface’ by K.I. Matveev, T.J. Burnett, and A.E. Ockfen [Ocean Engineering 36 (12–13) 891–1038 (September 2009)]”
No full textTransfer of a work by e-mail: copyright aspect
No full textE-mail gives the opportunity to send a work of science, literature and art to one or more addressees. Russian copyright law does not allow us to make an unambiguous conclusion about the legitimacy of such use of a work. Purpose: to determine the legal regime of the transfer of works protected by copyright through e-mail. Methods: method of formal logic, systematic structural and formal dogmatic methods are used in the analysis. The article presents two approaches to the problem under consideration. Article 1270 of the Civil Code of the Russian Federation is devoted to the contents of the exclusive copyright. This article establishes an open list of methods to use a work. Accordingly, we can make a logically correct, but legally dubious conclusion that any emailing of a work is illegal. This logic is based on the questionable legal technique of art. 1270 of the Civil Code of the Russian Federation. The author of the paper believes that the second approach is correct. According to this approach, the content of exclusive copyright should be limited to the methods to use a work that is specified in art. 1270. Emailing of a work includes two legally significant actions with such a work: 1) the creation of an electronic copy of a work; 2) sending this copy via the information and telecommunications network as an electronic message to a specific address. The first action is the reproduction of a work. The second action is the communication to the public. The transfer of a work by e-mail is the communication to the public if access to such a work can be obtained by a significant number of persons who do not belong to the usual family circle
Recommended from our members
Demonstration of acoustic instability in resonators with heat addition and mean flow
No full textThermoacoustic instabilities can arise in systems where unsteady heat release is favorably coupled with acoustic pressure oscillations. A modified Rijke tube with segments having different sections is found to have lower threshold levels of heat addition rate needed for exciting the fundamental acoustic mode of the tube. Experiments indicate that about 115 W of heating power is required to produce sound in the 90 cm long segmented tube, while over 230 W is needed in 60 cm long and 90 cm long tubes with constant-area cross sections. One of the causes for lowering the threshold of heat addition rate is due to a significant reduction of the resonator natural frequency. The presented results suggest an importance of including the system geometry details into analysis of practical devices prone to thermoacoustic instabilities. v Two types of acoustic energy harvesters are also tested and demonstrated in this study. Tonal sound is excited by heat addition or vortex shedding/impinging in the presence of mean flow in the resonator. The sound generated within the resonator is partially converted into electrical energy by using a piezoelectric disk with a brass back plate. One of the systems, a thermoacoustic engine, generated a maximum electric power of 0.446 mW at a resistance of 14.8 kΩ. The baffled tube with mean flow produced more than 0.5mW of electric power at a resistance of 10 kΩ and mean velocity of 2.6 m/s. Optimization of the system geometry and piezoelement are required in order to increase the power output
Recommended from our members
Development of small-scale thermoacoustic engine and thermoacoustic cooling demonstrator
No full textThermoacoustics is a science and technology field that studies heat and sound interactions. Sound waves in any fluid consist of coupled pressure, motion, and temperature oscillations. When the sound travels through a narrow channel, an oscillating heat flow between the fluid and the channel's wall becomes significant. The present study deals with the effects of thermoacoustic cooling with closed and open ended tubes and also investigates the performance of a small-scale thermoacoustic heat engine. The first part of this document presents the design, construction, and testing of a miniature standing-wave thermoacoustic heat engine. The main objective was to build and test a miniature heat engine without moving parts. Recorded parameters included the temperature difference across the stack and the corresponding acoustic pressure amplitude of the sound produced by the engine. The system was also tested for different stack materials and tube lengths. The most efficient system is described in detail in this document. The critical temperature difference across the stack was measured to be approximately 350°C for the 5.8 cm engine and 250°C for the 9.3 cm engine. The average acoustic RMS pressure of the sound produced was about 2.7 Pa at 30 cm from the engine for both lengths and the frequency of the sound was about 1.4 kHz for the 5.8 cm engine and about 1 kHz for the 9.3 cm engine. The second part of this document presents the effects of thermoacoustic cooling with closed and open ended tubes. The position of the stack and sound frequencies were varied to establish the most effective configuration. For each configuration, the pressure amplitude inside the tube and the sound frequency were the controlled parameters, and the temperature difference across the stack was measured. The experimental results of the thermoacoustic cooling system are compared to the theoretical results. For the closed-end system the temperature of the top of the stack was higher than the bottom and for the open-end system the temperature of the top of the stack was lower than the bottom. The maximum temperature difference was about 32°C for the closed-end and 16°C for the open-end
Numerical Modeling of Multi-Surface Planing Hull Hydrodynamics Using Source-Based Boundary Element Method
No full textThesis (Ph.D.), Mechanical Engineering, Washington State UniversityA source-based boundary element method (BEM) built on the potential flow theory is developed to study hydrodynamic characteristics of multi-surface planing hulls. Initially, both 2D and 3D numerical models are implemented and validated. Upon validation, the numerical model is applied for three specific hull types to predict their hydrodynamic properties. Firstly, the hydrodynamic performance of a stepped hull with variable deadrise angles is investigated. Secondly, the hydrodynamic inference effect on a symmetric catamaran hull is studied. And lastly, the hydrodynamic parameters are analyzed for the asymmetric catamaran setup.
The validation results are presented for the lift coefficient, center of pressure, water surface elevation around the hull, and pressure coefficient. Numerical results are compared with those found in the technical literature. Parametric calculations are carried out for a stepped hull with variable deadrise angles in two-speed regimes and the results are shown for hydrodynamic characteristics of the hull. For the catamaran design, the hydrodynamic interaction between hulls planing parallel to each other is known to become significant when the spacing between hulls is sufficiently small. To investigate this interference effect, calculations are carried out for symmetric hulls in variable speed regimes at different spacings, hull aspect ratio, and deadrise angles. Again, for asymmetric planing hulls, the numerical results are validated with available experimental data and empirical correlations. Parametric calculation results are presented for the lift coefficient and the center of pressure for variable hull geometry, spacings, and speed regimes.
It was observed that the wetted surfaces of both fore hull and aft body of the stepped hull have a direct impact on hydrodynamic forces. The downstream shape of the air-ventilated cavity changes drastically for variable aft body compared to the variable fore hull. For the catamaran hull, the interaction effect on the lift is stronger for longer hulls and larger deadrise angles at both moderate and high Froude numbers. The smaller spacings between two demi-hulls yield higher impact on different hydrodynamic parameters. Similarly, for asymmetric catamaran configuration, the lift coefficient is found to increase at smaller hull spacings. However, it decreases at higher Froude numbers and higher deadrise angles.Washington State University, Mechanical Engineerin
- …
