Experimental Investigation of the Effects of Acoustic Waves on Natural Convection Heat Transfer from a Horizontal Cylinder in Air

Heat transfer is a critical part of engineering design, from the cooling of rocket engines to the thermal management of the increasingly dense packaging of electronic circuits. Even for the most fundamental modes of heat transfer, a topic of research is devoted to finding novel ways to improve it. In recent decades, investigators experimented with the idea of exposing systems to acoustic waves with the hope of enhancing thermal transfer at the surface of a body. Ultrasound has been applied with some success to systems undergoing nucleate boiling and in single-phase forced and free convection heat transfer in water. However, little research has been done into the use of sound waves to improve heat transfer in air. In this thesis the impact of acoustic waves on natural convection heat transfer from a horizontal cylinder in air is explored. An experimental apparatus was constructed to measure natural convection from a heated horizontal cylinder. Verification tests were conducted to confirm that the heat transfer could be described using traditional free convection heat transfer theory. The design and verification testing of the apparatus is presented in this work. Using the apparatus, experiments were conducted to identify if the addition of acoustic waves affected the heat transfer. For the first set of experiments, a 40 kHz standing wave was created along the length of the heated horizontal cylinder. While our expectation was that our results would mirror those found in the literature related to cooling enhancement using ultrasound in water (cited in the body of this thesis), they did not. When a 40 kHz signal was used to actuate the air surrounding the heated cylinder assembly, no measurable enhancement of heat transfer was detected. Experiments were also performed in the audible range using a loudspeaker at 200 Hz, 300 Hz, 400 Hz, 500 Hz, and 2,000 Hz. Interestingly, we found that a 200 Hz acoustic wave causes a significant, measurable impact on natural convection heat transfer in air from a horizontal cylinder. The steady-state surface temperature of the cylinder dropped by approximately 12℃ when a 200 Hz wave was applied to the system

Molecular dynamics simulations of ultrathin water film confined between flat diamond plates

Molecular dynamics simulations of ultrathin water film confined between atomically flat rigid diamond plates are described. Films with thickness of one and two molecular diameters are concerned and TIP4P model is used for water molecules. Dynamical and equilibrium characteristics of the system for different values of the external load and shear force are investigated. An increase of the external load causes the transition of the film to a solidlike state. This is manifested in the decreasing of the diffusion constant and in the ordering of the liquid molecules into quasidiscrete layers. For two-layer film under high loads molecules also become ordered parallel to the surfaces. Time dependencies of the friction force and the changes of its average value with the load are obtained. In general, the behaviour of the studied model is consistent with the experimental results obtained for simple liquids with spherical molecules.Comment: 10 pages, 9 figures, PDFLaTe

Equation of State for a van der Waals Universe during Reissner-Nordstrom Expansion

In a previous work [E.M. Prodanov, R.I. Ivanov, and V.G. Gueorguiev, Reissner-Nordstrom Expansion, Astroparticle Physics 27 (150-154) 2007], we proposed a classical model for the expansion of the Universe during the radiation-dominated epoch based on the gravitational repulsion of the Reissner-Nordstrom geometry - naked singularity description of particles that "grow" with the drop of the temperature. In this work we model the Universe during the Reissner-Nordstrom expansion as a van der Waals gas and determine the equation of state.Comment: 13 pages, 2 figure

Study of friction of Ag and Ni nanoparticles: An atomistic approach

ࠗ w This paper contains enhanced objects available on the Internet at http://pubs.acs.org/JPCC. Manipulation of metal nanoparticles using atomic force microscopy is a promising new technique for probing tribological properties at the nanoscale. In spite of some advancements in experimental investigations, there is no unambiguous theoretical treatment of processes accompanying the movement of metallic nanoislands adsorbed on a flat surface, and additional research is required. In this paper, we describe computer experiments based on classical molecular dynamics in which the behavior of silver and nickel nanoparticles interacting with a graphene sheet and sheared with constant force is studied. Frictional force acting on the nanoislands is measured as a function of their size. It is shown that its average value grows approximately linearly with contact area, and slopes of linear fits are close to the experimentally observable ones. The dependence of the friction force value and of the shape of the measured friction curves on the type of metal atom is revealed, and its possible reasons originating from atomistic background are discussed

Control of the Respiratory Diseases in a Pig Herd Using Data of the Respiratory Organs Examination of Fattening Pigs at a Slaughterhouse

In everyday farming practice, assessment of economical impact of respiratory diseases at herd level relies on the following information: data records on the diseases within the herd, productivity and slaughterhouse records. The data available from the slaughterhouse encompass the number and percentage of low weight pigs, number of diseased animals, the severity of lesions observed at slaughter as well as the amount of discarded organs and carcasses. The aim of this investigation is to improve the assessment of health status of pigs at herd level and design programs for the control of respiratory syndrome in swine based on the analysis of the data collected at slaughter line. In the slaughterhouse, the thoracic cavity organs from 105 fatlings that have reached the slaughter body mass, 20 underweight fatlings and 20 underdeveloped piglets were examined. The weight of both half-carcasses was measured. Tissue samples of altered organs (lungs, mediastinal lympho nodes, tonsils) were collected and subjected to bacteriological analysis. The average weight of both half-carcasses was 81.54kg in fatteners with full slaughter body mass, and 58.29kg and 14.95kg in low-weight fatlings and piglets, respectively. Changes affecting 10% of lung tissue were established in 9 animals, 11-20% in 10 and 21-32% in 10 fatlings. Pathological process is characterized by hepatization of lung tissue, inflammation of the pleura or, even more frequently, adhesions between the visceral and parietal pleura and pericardium. In underweight fatlings, the rates of lung changes were 20% in 5, 11-30% in 3, 40% in 4, and 40% in 6 animals. Applying bacteriological testing, the following microorganisms were isolated: Haemophilus parasuis, Arcanobacterium pyogenes, and Pasteurella multocida. The examination performed at the slaughter line strongly suggested the necessity of designing a new, updated vaccination program taking into consideration the causative agents and vaccination schedule

Swine Dysentery: Practical Observations, Control And Diagnostics

Swine dysentery is a severe mucohemorrhagic enteric disease of pigs which has a large impact on pig production, with important losses caused by mortality and suboptimal performance. The causative agent is Brachyspirahyodysenteriae. The aim of the paper was to evaluate all the available data on B. hyodysenteriae presence on swine farms in Vojvodina region. The material for this research included five swine farms, where certain disorders and health problems in weaned, grower and fattening pigs were detected. Depending on the specificity of each evaluated case and available material, the applied research methods included: anamnestical and clinical evaluation, gross pathological examination, standard bacteriological testing for detection of the presence of aerobic and anaerobic bacteria in the tissue samples derived from diseased and/or died pigs. Besides this, in some cases the molecular diagnostic method (RT-PCR) was included. Swine dysentery is a common and important endemic problem in many swine farms in Vojvodina. On endemically infected swine farms transmission mainly occurs by ingestion of infected faeces. All the observed factors affecting disease persistence and transmission on the farm are thoroughly analysed and discussed. Finally, current prophylactic and therapeutic approaches to fight against disease are described

Russian institute for advanced study as a new form of training of highly trained teaching staff

Introduction: The aim of the paper is the analysis of role and capabilities of the Russian Institute for Advanced Study under Moscow State Pedagogical University in preparation of the top qualification scientific and teaching staff, possessing not only high potential in the narrow specialisation, but also inter-And transdisciplinary knowledge. The necessity for such staff is caused by rapid growth of scope and rates of new scientific knowledge accumulation, and, as a result, by development on their basis of new technologies in all sectors and by intensive introduction of such developments into all spheres of human activities. Materials and Methods: The processing of results of survey by the questionnaire method, as well as the synergistic and systemic approaches in their analysis and generalization, constituted the methodological basis for this study. Results: by analysis and generalisation of survey results it was shown that the Russian Institute for Advanced Study is unique form of training of top qualification scientific and teaching staff. The most important role of the Russian Institute for Advanced Study functioning format in implementation for Institute's tasks is shown. During the work period at the Russian Institute for Advanced Study scientific and pedagogical employees are having unique possibility for finding non-standard approaches and methods for solving various problems, arising during projects implementation and which can't be solved due to formal limitations of the traditional education system. Discussion and Conclusions: it is shown that the structure and principles of the Russian Institutes for Advanced Study functioning provide preparation of scientific and pedagogical staff of the highest qualification. The requirement for expanding Institutes for Advanced Study network in Russia is discussed. The results obtained represent practical importance for researchers engaged in the analysis of inter-And transdisciplinary knowledge role in the training of scientific and pedagogical staff. Further studies in this area can be devoted to analysis and generalization of inter-And transdisciplinary approach in the training of highly qualified scientific and pedagogical staff

On subgroups of minimal topological groups

A topological group is minimal if it does not admit a strictly coarser Hausdorff group topology. The Roelcke uniformity (or lower uniformity) on a topological group is the greatest lower bound of the left and right uniformities. A group is Roelcke-precompact if it is precompact with respect to the Roelcke uniformity. Many naturally arising non-Abelian topological groups are Roelcke-precompact and hence have a natural compactification. We use such compactifications to prove that some groups of isometries are minimal. In particular, if U_1 is the Urysohn universal metric space of diameter 1, the group Iso(U_1) of all self-isometries of U_1 is Roelcke-precompact, topologically simple and minimal. We also show that every topological group is a subgroup of a minimal topologically simple Roelcke-precompact group of the form Iso(M), where M is an appropriate non-separable version of the Urysohn space.Comment: To appear in Topology and its Applications. 39 page

Correlation between the limit values of laboratory and clinical mycotoxicosis

Analysis of feed for the presence of fungi and mycotoxins is a request necessary to meet in order to ensure a healthy and economical production in livestock. These tests are related to legal regulation which prescribes the maximum legislated content (MLC), both for the presence of mycotoxins and the total number of fungi in certain feeds. Health problems that can occur during the production of animals are sometimes caused by the presence of mycotoxins in the feed. Laboratory testing is a good practice to confirm a suspicion, and allows timely treatment of contaminated feed. Potential problems arise under circumstances when there is a clinical outcome of mycotoxicosis and animal and laboratory findings suggest that the obtained values are below the level that is within the MLC. For these reasons, the subject of our research was to investigate the occurrence of mycotoxins and mold in feed, as well as the clinical presentation for animals that were fed with the feed with allowed values of these agents according to the recommended levels. The aim of this paper was to highlight the problems associated with clinical correlation of sick animals and laboratory findings, and suggest their overcoming. In the period of one year, a total of 176 samples of feed (complete mixture for broilers, corn and soy products) were examined for the presence of fungi, 106 samples were examined for the presence of mycotoxins and 26 flocks of broilers and turkeys were clinically observed. Standard methods were used for isolation of molds and the ELISA test was used for the detection of mycotoxins. Clinical and pathomorphological observation of the flocks was done to determine the natural indicators of production. Studies indicated a problem because clinical and pathomorphological findings in some cases were not correlated with laboratory findings of molds and mycotoxins in the feed, and in some cases it did not necessarily mean that the animals were healthy. Synergism and cumulative effects of mycotoxins, on the one hand, and the characteristics of each species and product category on the other hand, can create specific circumstances that can lead to disease and can increase even though the values prescribed by legislation have been met. [Projekat Ministarstva nauke Republike Srbije, br. TR 031071