NUMERICAL ANALYSIS OF ROLLER BEARING

The aim of this paper is to detail the creation of a large tapered roller bearing model with flexible body cages in the Adams program suite for subsequent dynamic analysis and to obtain information about kinematic and dynamic relationships of steel and plastic cages under various operating conditions. The bearing model was made to closely resemble its real-life counterpart, which allows us to estimate load conditions, dynamic conditions of individual bearing parts and interactions between them

Theoretical study of heat conduction in the multi-disc brake integrated into the drive wheel AGV during braking

This paper is focused on the theoretical study of heat conduction in the multi-brake system of the automated guided vehicle (AGV). The study aims to compare the amount of heat generated during braking from 10 m/s until a stop in a brake system based on organic and ceramic friction material. The theoretical study of heat conduction is solved in Matlab computational software using a derived Fourier partial differential equation for nonstationary heat conduction. The results of the simulation of the heat conduction are shown in the diagrams and indicate not only the temperature dependence in the period during braking from a speed of 10 m/s to a stop but also the amount of heat accumulated in the steel disc during braking. The simulation results show that braking in both brake systems generates approximately the same amount of heat. The difference occurs in the period of thermal activity, which was influenced by the length of the braking distance. This is caused by a coefficient of friction that significantly affects the final braking result. Finally, it can be stated that the brake system based on organic material must be equipped with a steel disc with a minimum thickness of 8 mm. This is because the brake system based on organic friction material has a set temperature limit of 160 degrees Celsius. The results presented in this study will help an engineer constructor to choose the right procedures and parameters of geometry for designing the mentioned braking system for the considered AGV

Influence of Burner Nozzle Parameters Analysis on the Aluminium Melting Process

The paper presents the results of the optimisation of burner nozzle diameters during the combustion of natural gas under the conditions of increasing oxygen concentrations in the oxidizer in aluminium melting processes in drum rotary furnaces. The optimisation of outlet nozzle diameters was performed employing the method of experimental measurements, the results of which can be used for aluminium melting in hearth furnaces. The measurements were carried out using an experimental upstream burner with 13.5 kW input power. The monitored oxygen concentrations in the oxidizer ranged from 21% to 50%. The measurements were performed and evaluated in two variations of the burner configuration (geometry). In the first study, the impact of the enriched oxidizer on the melting of aluminium ingots was evaluated with the defined diameter of the air nozzle, which resulted in a reduction of the aluminium charge melting time by 50% at 45.16% oxygen concentration in the oxidizer, thus achieving savings in the consumption of fuel used for melting. In the second study, the diameter was optimised depending on the combustion rate of the natural gas and oxidizer mixture. The optimisation of the nozzle parameters resulted in the reduction of the charge melting time by 23.66%, while the same 25% enriched oxidizer was used. With the rise of the enrichment level to 35%, further reduction by approximately 12% was observed. The measurement results prove considerable influence of the parameter (geometry) optimisation of the outlet nozzles and oxidizer enrichment. Appropriately selected parameters of the burner can contribute to achieving comparable results at a lower enrichment of the oxidizer. The obtained results demonstrate the intensification of the heat transfer in the current thermal aggregates. The research conclusions confirm that oxygen-enhanced combustion and modification of existing burners reduces the specific energy consumption on the process and reduces CO2 emissions

Effect of GnRH (Lecirelinum) on some quality parameters of rabbit ejaculate

The aim of this study was to evaluate the effect of two concentrations of GnRH in insemination doses on selected quality parameters of rabbits ejaculate in vitro. Insemination doses (ID) were diluted to a concentration of 50 x 106 spermatozoa in ID (0.5 ml). Subsequently ID was divided into 3 samples (control - C, experiment 1, experiment 2). Implementor GnRH (Lecirelinum – commercial product Supergestran, Ferring Pharmaceuticals, the Czech Republic) was added to experimental insemination dose samples at concentrations as follows: experiment 1 to 0.2 ml (5 mg) GnRH / ID and experiment 2 to 0.3 ml (7.5 mg) GnRH / ID. Experimental samples were compared with the control sample. For the assessment of spermatozoa motility the CASA (Computer-Assistend Sperm Analysis) system SpermVision (MiniTüb, Tiefenbach, FRG) with a microscope Olympus BX 51 (Olympus, Japan) was used. Monitored spermatozoa parameters were motility (%), progressive motility (%), velocity (μm/s), curvilinear velocity of motility (μm/s) and beat cross frequency. In experimental samples (experiment 1, 2) increase of the spermatozoa motility values was detected in time periods of 1 and 3 hours (1 hour – C: 47.30 ± 7.99%, experiment 1: 86.39 ± 5.60%, experiment 2: 72.48 ± 3.80%, 3 hours – C: 57.09 ± 23.36%, experiment 1: 89.42 ± 2.41%, experiment 2: 63.92 ± 12.65%) and decrease over a period of 6 hours (C: 64.65 ± 8.60%, experiment 1: 35.26 ± 5.22%, experiment 2: 50.08 ± 8.27%). Progressive spermatozoa motility within time periods of 1 and 3 hours showed a similar trend as spermatozoa motility (1 hour – C: 30.50 ± 7.35%, experiment 1: 79.18 ± 6.58%, experiment 2: 59.85 ± 6.03%; 3 hours – C: 42.06 ± 22.69%, experiment 1: 82.31 ± 3.64%, experiment 2: 44.45 ± 12.01%) and decreased over a period of 6 hours (C: 56.34 ± 8.88%, experiment 1: 23.36 ± 5.95%, experiment 2: 39.07 ± 11.17%). Spermatozoa curvilinear velocity in experiment 1 reached after 1 hour 82.26 ± 4.47 μm/s, after 3 hours 68.40 ± 3.20 μm/s, after 6 hours 58.21 ± 3.89 μm/s; in experiment 2 was after 1 hour 62.00 ± 4.33 μm/s, after 3 hours 44.37 ± 9.19 μm/s and after 6 hours 52.73 ± 9.10 μm/s, in control group after 1 hour 71.86 ± 8.19 μm/s, after 3 hours 62.35 ± 7.89 μm/s and after 6 hours 73.93 ± 8.18 μm/s. Lower concentration of the implementor (1 to 0.2 ml GnRH / ID) ​​increased level of motility, progressive motility, velocity and curvilinear velocity of motility in the time period 1 and 3 hours after GnRH implementor application compared with the control sample. In 6 hours after application only lower changes of monitored parameters has occurred. The effect of GnRH under in vivo conditions may vary significantly comparing with results obtained in vivo

Impact of oxygen enhanced combustion of natural gas on thermal efficiency of combustion aggregate

The aim of the present article is to present the achieved results on the experimental combustion aggregate. In the experimental measurement, the increased of the oxygen concentration in the oxidizing agent in the combustion of natural gas has been used. The results presented in this article are focused to achieve the thermal efficiency of the device, which is expressed by useful heat of the combustion aggregate. Part of the article is the analysis of the heating heat exchanger based on heat flow by convection and radiation and CFD mode of heat exchange

Analyzing the Formation of Gaseous Emissions during Aluminum Melting Process with Utilization of Oxygen-Enhanced Combustion

Oxygen-enhanced combustion (OEC) is a useful method for improving the efficiency of thermal plants and for decreasing greenhouse gas (GHG) emissions. Basic and modified burner designs utilizing OEC in the aluminum melting process in a rotary tilting furnace were studied. A combined approach comprising experimental measurement and simulation modeling was adopted aimed at assessing GHG emissions production. Reduction of up to 60% fuel consumption of the total natural gas used in the laboratory-scale furnace was achieved. The optimal oxygen concentration in the oxidizer regarding the amount of total GHG emissions produced per charge expressed as CO2 equivalent was 35% vol. Its further increase led only to marginal fuel savings, while the nitrogen oxide emissions increased rapidly. Using the modified burner along with OEC led to around 10% lower CO2 emissions and around 15% lower total GHG emissions, compared to using a standard air/fuel burner. CFD simulations revealed the reasons for these observations: improved mixing patterns and more uniform temperature field. Modified burner application, moreover, enables furnace productivity to be increased by shortening the charge melting time by up to 16%. The presented findings demonstrate the feasibility of the proposed burner modification and highlight its better energy and environmental performance indicators, while indicating the optimal oxygen enrichment level in terms of GHG emissions for the OEC technology applied to aluminum melting

STRUCTURAL CHANGES IN THE RAT TESTIS CAUSED BY DIAZINON AND SELENIUM

<div style="mso-element: frame; mso-element-frame-width: 498.1pt; mso-element-frame-height: 318.1pt; mso-element-frame-vspace: 3.1pt; mso-element-wrap: around; mso-element-anchor-vertical: page; mso-element-anchor-horizontal: page; mso-element-left: 52.45pt; mso-element-top: 55.2pt; mso-height-rule: exactly;"><span style="font-size: medium;"><p class="MsoNormal">The aim of this study was to find the structural changes in the rat testis after a diazinon, selenium and their combined administration. The testis structural changes after the diazinon intraperitoneal administration of 20 mg/kg b.w., selenium 2 mg/kg b.w. and both diazinon 20 mg/kg b.w. and selenium 2 mg/kg b.w. were evaluated by histological and morphometric methods in light microscopy. 36 hours after the diazion i.p. administration, the vacuolization of the seminiferous epithelium, evacuation of germ cells into the tubule lumen, epithelium necrosis and disintegration, interstitium extension and fibrotization were observed. The germ cells released from the basal lamina and subsequently they were visible in the tubule lumen. Blood vessels were damaged and morphometric analysis have shown their significant dilatation (P<0.05). Diazinon causes the damage of the germinal epithelium in the testes leading to the spermatogenesis failure. The infertility can then appear. In selenium treated group disintegration of cellular associations in the seminiferous epithelium, damaged and separating spermatids lines, reduced spermatogenesis and significant vacuolization of seminiferous epithelium (P<0.0001) were observed. Similar changes as in selenium threated group occured, significant vacuolization of seminiferous epithelium (P<0.05) was seen. In combined diazinon and selenium treated group protective effects of selenium in seminiferous epithelium and interstitium were noticed. Further investigation of diazinon and selenium is needed to practical use this results.</p><p class="MsoNormal">&nbsp;</p><p class="MsoNormal"><span style="font-size: 12px;"><strong>doi:10.5219/44</strong></span></p> <p class="MsoNormal">&nbsp;</p></span></div

QUANTITATIVE AND STRUCTURAL CHANGES OF TESTIS AND SEMEN QUALITY PARAMETERS CHANGES CAUSED BY PERORAL ADMINISTRATION OF DIAZINON IN RATS

<div><table style="height: 641px;" border="0" cellspacing="0" cellpadding="0" width="664"><tbody><tr><td style="padding-top: 3.1pt; padding-right: 0cm; padding-bottom: 3.1pt; padding-left: 0cm;" height="641" align="left" valign="top"><div style="mso-element: para-border-div; border: none; border-bottom: solid windowtext 2.25pt; padding: 0cm 0cm 1.0pt 0cm;"><p class="MsoNormal" style="text-align: justify; text-justify: inter-ideograph; mso-layout-grid-align: none; text-autospace: none; border: none; mso-border-bottom-alt: solid windowtext 2.25pt; padding: 0cm; mso-padding-alt: 0cm 0cm 1.0pt 0cm; mso-element: frame; mso-element-frame-width: 498.1pt; mso-element-frame-height: 474.8pt; mso-element-frame-vspace: 3.1pt; mso-element-wrap: auto; mso-element-anchor-vertical: page; mso-element-anchor-horizontal: page; mso-element-left: 50.3pt; mso-element-top: 57.8pt; mso-height-rule: exactly;"><span style="font-size: 10.0pt;">The aim of this study was to find the quantitative and structural changes in the rat testis and changes of semen quality after a diazinon administration. METHODS: Rats&nbsp;received&nbsp;diazinon&nbsp;(99% purity) in&nbsp;thier drinking water (40&nbsp;mg</span><span style="font-size: 10pt; font-family: "Times New Roman","serif";">.l^-1</span><span style="font-size: 10.0pt;">) with free access. Age of&nbsp;rats&nbsp;at the beginning&nbsp;of the experiment&nbsp;was 30 days and experiment lasted for next 90 days. The histological samples were evaluated by histological and morphometric methods in light microscopy and the samples of semen were evaluated with CASA method. RESULTS: Disintergation of cellular associations in the seminiferous epithelium, germ cells evacuation into the tubule lumen and thier necrosis were mostly observed. Rarely vacuolisation and cracks of epithelium and fibrotisation of interstitial tissue were noted. Morphometric methods have shown extension of epithelium (P<0,01), reduction of&nbsp; tubule lumen (P<0,001) and dilatation of blood vessels (P<0,001). In CASA analysis elevation of all parameters were noted, with statistically significant increase of DSL, VSL, ALH. Dilatation of blood vessels will be probably one of the most significant finding in diazinon toxicity because changes in blood flow in the testis are the key factors of accurate physiological function of testis. The epithelium despite the serious disintegration of germ cells associations and release of these necrotised germ cells to the lumen was significantly extended. This fact indicates the self-reparation compensational function. The same tendency (stimulation effects) has been found in all analysed sperm parameters. It supports previous hypothesis. CONCLUSIONS: Diazinon in this design of experiment causes the disintegration of the germinal epithelium cells associations consequently leading to necrosis and release of these cells to the tubule lumen. Dilatation of blood vessels and unknown stimulation effect on sperm quality parameters are two other common effects of diazinon. We concluded that diazinon in our subchronic low dose test causes middle to moderate histological,&nbsp; morphometric and semen quality changes which were partially compensated with some unknown recovery mechanism. Otherwise,</span> <span style="font-size: 10.0pt;">subcellular structures and their functions may be damaged which can lead to subfertility. Further investigation of diazinon is needed for verification of our hypothesis.<br /><br /><strong>doi:10.5219/188</strong></span></p></div></td></tr></tbody></table></div