Vibration diagnostics of rotary equipment is one of the reliable methods for preventing accidents and predicting equipment life. This article will discuss the theoretical principles of the impeller’s fan bearings spectral analysis of vibration, as well as the method practical application.
In today’s automobile industry, the need to adjust the speed of the vehicle and stabilize the wheels control is still a task due to road conditions and traffic. The Anti-lock Braking System (ABS) is a tool used in automobiles to prevent wheels from locking while brakes are pressed. The objective of this work is the maintenance of the wheel slip value to a desirable slip ratio as the vehicle model is simulated using a fuzzy logic controller. The analyses are made based on the slip ratio, angular velocity and stopping time.
The paper present thermodynamic analysis of three-cylinder steam turbine, which operates in a combined cycle power plant. It is performed analysis of each turbine cylinder and of entire steam turbine. Comparison of steam turbine cylinders shows that intermediate pressure cylinder develops the highest real power and has the highest efficiencies while low pressure cylinder has the highest ideal (isentropic) power, the highest loses and the lowest efficiencies – therefore, improvement potential of the low pressure cylinder is the highest. Entire observed steam turbine has an energy efficiency equal to 86.58 % and exergy efficiency equal to 89.26 %, what is lower in
comparison to high power steam turbines from some conventional land-based steam power plants but also higher in comparison to low power marine steam turbines.
Micro-drilling (MD or мD) is type of machining (processing) technology used for the drilling of miniaturized parts of small diameter in micro-scale, ie. diameter in a range of a few microns to several hundred microns. In paper is given the dependence of axial efforts and torque on different modes of depth of drilling in micro-drilling with micro-drills from solid alloy VK60M with standard rake angle ω=300 and f=0.01 [mm/turn
In recent years, the world of material science has observed a wide range of applications of Titanium alloys; especially Ti6Al4V, a grade-V alpha-beta titanium alloy; in biomedical instruments, automobile engineering, aerospace engineering, marine engineering, etc. Shaping this material by conventional machining processes is very difficult because of some of its properties, like high strength, high chemical affinity, etc. That’s why non-conventional machining processes, like electro-discharge machining (EDM), have been applied to shape the material. Past researches revealed that in EDM, both the quality of machining and machining rate deteriorate due to accumulation of debris in the machining zone. The present research has been focused to achieve better machining rate and machining quality by incorporating conical tool and vibration in the workpiece. The effects of, both vibration of workpiece and shape of the tool on material removal rate (MRR) and Diametric Over-cut (DOC), have been studied through a planned set of experiments. The result shows that MRR almost doubled using vibration assisted EDM. However, the DOC also increased due to vibration. On the other hand, the use of the conical tool resulted in increased MRR and a reduced DOC. The paper also includes analysis of the effects of peak-current and pulse-ontime on MRR and DOC.
The paper presents experimental results of hardening of the meat comminutor knives by using the pulse-plasma method. A search for existing methods for increasing the wear resistance of knives of meat-cutting machines has been carried out. The determination of the increase in wear resistance of the meat comminutor knives has been carried out according to the following stages: knives hardening; knives testing on the meat comminutor with the simultaneous execution of control prints; determination of the radius of blade curvature using an optical microscope and processing of research results. It is experimentally established that the use of the proposed method allows to increase the wear resistance of the meat comminutor knives by 4 times. Also, during the study, the optimal hardening modes of the meat comminutor knives are determined. The graphical dependence of the amount of knives wear on the presence and regime of hardening treatment is presented.
During the lifelong maintenance of low-voltage electrical installations in any facility special attention must be given to firecausing failures, which cannot be detected by conventional protection devices (miniature circuit breakers, fuse-links, residual current devices, etc.). Such failures are most often caused by poor electrical contacts. International regulations and standards, which define periodic verification of the quality of low-voltage electrical installations, do not contain procedures by which a poor electrical contact would be detected at an early stage. However, one of the techniques used for this purpose today is performing preventive thermographic inspections (a standard covering this area is available only in the USA). By such inspections a poor electrical contact which creates prerequisites for the occurrence of an initial fire in a low-voltage electrical installation can easily and effectively be detected. Detected failures and irregularities can most frequently be eliminated by simple interventions of electricians or facility technical services. Experience from a large number of periodic verifications of the quality of low-voltage electrical installations in industrial and administrative facilities, conducted by personnel of the Laboratory for testing low-voltage electrical and lightning protection installations at the School of Electrical Engineering in Belgrade, showed that many dangerous failures would not be detected without performing preventive thermographic inspections. Several practical examples of such failures, detected in low-voltage electrical installations in industrial and administrative facilities during preventive thermographic inspections, are presented and analysed. The procedure of performing preventive thermographic inspections within periodic verifications of the quality of low-voltage electrical installations, as well as the explanation for proper interpretation of the measurement results based on the ΔТ and absolute temperature criteria, are also given in this paper.
Phenols are widely distributed in various plants and plant-derived foods. Currently, there is an increasing interest in their application as food supplements. In this study we performed a virtual screening to identify potential molecular targets of phenolic compounds derived from medicinal plants known for their antioxidant and anticancer effects. A dataset of 75 phenols, reported in the literature and a virtual library of 7770 unique drug compounds, extracted from the DrugBank database (https://www.drugbank.ca/) were used. Multi-conformer structure databases were created using OpenEye OMEGA, shape- and chemical-based overlays of the conformers were performed in OpenEye ROCS (https://www.eyesopen.com/). As a result of the virtual screening, followed by data filtration and analysis, two bacterial enzymes, responsible for DNA replication, were suggested as potential novel targets of a plant-derived hydroxyanthraquinone. This research allows outlining the potential receptor-mediated pharmacological mechanisms of phenolic compounds and aims to be a first step in the development of in silico protocol for their prioritisation as healthy dietary supplements.
Researches in this paper included synthesis and characterization of bismuth telluride single crystal doped with arsenic, obtained using Bridgman method. Compounds based on bismuth telluride are very important materials for thermoelectric refrigerators and devices for electricity production. For the monocrystal characterization, SEM – EDS, Hall and Van der Pauw method were used. The results presented in paper show the synthesis of monocrystal ingot, BiTeSe doped with arsenic. An analysis of energy dispersive spectrometry (EDS) was used to determine the chemical composition of the samples studied, as well as checking and confirming the homogeneity of the samples. Measurements of X-ray diffraction (XRD) showed that the resulting crystalline ingot represent a single crystal and confirm the compound of Bi2Te3 type. Mobility, concentration, resistivity/conductivity, of majority of charge bearers and Hall coefficient of single crystal, were determined using a Hall Effect measurement system based on the Van der Pauw method. For the sample of BiTeSe doped with arsenic Hall effect was measured at room temperature with an applied magnetic field strength of 0.37 T at different current intensities. Further characterization of the BiTeSe sample doped with arsenic was not performed, because the expected improvement in the mobility of this sample in comparison with the theoretical value of the n type Bi2Te3, was not obtained.
Beehive made of ceramic is a relatively novel concept in the feed of the beekeeping industry. One of the reasons behind the idea of changing the classical construction material of the beehives is the relatively better thermal conductivity of the ceramic material in comparison with the wooden. Previous field observations show that in wintertime the temperature in the ceramic beehive is with 1oC to 2oC warmer than the temperature measured in a wooden beehive from the same field. The present study aims to examine the thermographic characteristics of a ceramic beehive and to compare them with the most spread wooden type of hives. For the purpose, it was conducted a thermographic diagnostic of three beehives (two ceramic and one wooden) from the same field. The measurement is conducted with a thermal imaging infrared camera. For the analysis is used a licensed software FLIR Reporter Pro. The results of the comparative analysis show that in terms of balanced thermal distribution and creating a better internal environment, the ceramic beehives outperform the wooden one. What is more, the higher porosity of the ceramic material is proved to be a factor in the provision of a balanced thermal environment for the bee family.
This publication traces the peculiarities of metal powder production for powder metallurgy. Of the variety of methods, particular attention is paid to those that are most widely used in practice – reduction and powdering methods. Metallurgical photo of iron powders obtained by different technological processes are presented, as well as tables with the basic technological properties of iron powders obtained by reduction and powdering.