Numerical study of transient three-dimensional heat conduction problem with a moving heat source

A numerical study of transient three-dimensional heat conduction problem with a moving source is presented. For numerical solution Douglas-Gunn alternating direction implicit method is applied and for the moving heat source flux distribution Gaussian function is used. An influence on numerical solution of input parameters figuring in flux boundary conditions is examined. This include parameters appearing in Gaussian function and heat transfer coefficient from free convection boundaries. Sensitivity of cooling time from 800 to 500°C with respect to input parameters is also tested

Eksperimentalna analiza i MKE modeliranje vibracija reznog alata

Presented in this paper is a comparative analysis of vibrations, measured during machining process and modelled by FEM. Moreover, microscopic structure of chip cross section was analyzed in order to establish the frequency of lamellae generation and its influence on the total level of vibrations of the cutting tool. Based on the results thus obtained, a method was proposed which allows determination of tool wear degree through separation of reliable indicators from the high-frequency spectrum of the measured vibration signals. This investigation showed that the change of chip segmentation frequency significantly influences the output vibration signal within the high-frequency spectrum, and is a function of tool wear degree.U radu je dat usporedni pregled vibracija reznog alata izmjerenih u procesu obrade i modeliranih primjenom metode konačnih elemenata (MKE). Također, analizirana je mikroskopska strukture poprečnog presjeka odvojenih čestica sa ciljem utvrđivanja frekvencije stvaranja lamela i njihovog utjecaja na ukupnu razinu vibracija alata za obradu. Prikazom dobivenih rezultata postavljene su osnove za verifikaciju predložene metode određivanja stanja istrošenosti alata izdvajanjem pouzdanih pokazatelja iz visokofrekventnog dijela spektra signala izmjerenih vibracija. Provedeno istraživanje pokazalo je evidentan utjecaj promjene frekvencije segmentacije odvojenih čestica na odziv signala vibracija u visoko-frekventnom dijelu spektara, te ovisnost o promjeni stupnja istrošenosti reznog alata

Reaction of a 3-aryilidene-2-thiohydantoin derivative with polymeric trans-[CuCl2(DMSO)(2)](n) complex: unexpected isomerization to dinuclear cis-[{CuCl(DMSO)(2)}(mu-Cl)](2)

The 3-arylidene-2-thiohydantoin derivative, 3-[(2-hydroxybenzylidene)amino]-2-thioxoimidazolidin-4-one, was synthesized in a two-step condensation reaction of 2-hydroxybenzaldehyde, thiosemicarbazide and ethyl chloroacetate. The ligand was structurally characterized by NMR and IR spectroscopy, as well as by elemental analysis. In the reaction of the well-known polymeric trans-[CuCl2(DMSO)(2)](n) complex with the polydentate thiohydantoin type ligand, instead of the corresponding copper thiohydantoin complex, unexpectedly, the dinuclear cis-[{CuCl(DMSO)(2)}(mu-Cl)](2) complex (1) was formed predominantly as the final stable product. The structure of the complex 1 was confirmed by single crystal X-ray diffraction analysis. The cis-complex is obtained through assisted isomerization of the trans-form, in which the thiohydantoin derivative has a crucial role

Assessment of air temperature trend in South and Southeast Bosnia and Herzegovina from 1961 to 2017

Recent climate change has been caused by interaction of natural processes and the anthropogenic factor. In turn, it incites the pronounced natural and socio-economic changes. It is the air temperature that plays a pertinent role in understanding the climate change problem. Southeast Europe, including Bosnia and Herzegovina (B&H), is highly relevant for the observations of regional differences in changes of air temperature regime. From the regional-geographical point of view, South and Southeast B&H cover 26.5% (13.568 km²) of B&H territory (51.209 km²). It is from south and southeast that the Mediterranean impacts from the Adriatic Sea penetrate into the defined region, which further affects the variability of climate conditions in B&H. The paper presents trends in three parameter categories: mean annual, mean maximum, and mean minimum air temperatures in the territory of South and Southeast B&H. The aim of the paper is to demonstrate the likely climate change based on air temperature trends. Methodologically, temperature trends were processed by using the Mann-Kendall trend test. For the purpose of the analysis, available data from four meteorological stations in South and Southeast B&H for a 56-year period were used. Based on the obtained results, a statistically relevant positive trend was observed in all twelve time series. According to the analyzed trends, the increase of air temperature was dominant in the target area. The application of Geographical Information System (GIS) tools indicated the presence of regional differences in air temperature distribution. An evident phenomenon is the combined impact of the orography of the region and the maritime influence. The occurring climate change affects specific social sectors, so the problem must be addressed properly. Another pertinent fact is that the climate change problem has not been adequately analyzed in the strategic documents in B&H

Analiza formiranja PVB-SiO2 nanokompozitnih vlakana pomoću elektrospining procesa

The poly (vinyl butyral)-silica (PVB-SiO2) nanofibers were obtained by the electrospinning process. The experiments were carried out with PVB solution in concentration of 10 wt.% where ethanol was used as the solvent. The silica nanoparticles were added in the solution in different contents of 1, 3 and 5 wt.% SiO2 and nanoparticles were modified with γ-aminopropyltriethoxysilane (AMEO silane). The impacts of the parameters of the electrospinning process and the silica nanoparticles on the produced PVB-SiO2 nanocomposite fibers were tested. The structures of the PVB-SiO2 nanocomposite fibers were investigated using optical microscopy and scanning electron microscopy (SEM). The morphology and distribution of the resulting nanofibers were analyzed using the software Image-Pro Plus. .Poli (vinil butiral)-silika (PVB-SiO2) nanovlakna su dobijena metodom elektrospininga. Eksperimenti su izvedeni u rastvoru 10 mas.% PVB-a u etanolu koji je korišćen kao rastvarač. Nanočestice silike su dodate sa različitim sadržajem od 1, 3 i 5 mas.% SiO2 i modifikovane γ-aminopropiltrietoksi silanom (AMEO silanom). Istražen je uticaj procesnih parametara elektrospininga na nanokompozitna vlakna PVB-SiO2. Struktura PVB-SiO2 nanokompozitnih vlakana je proučavana pomoću optičke mikroskopije i skenirajuće elektronske mikroskopije (SEM). Morfologija proizvedenih nanokompozitnih vlakana i njihova raspodela je analizirana u Image Pro Plus softveru.

NUMERICAL STUDY OF TRANSIENT THREE-DIMENSIONAL HEAT CONDUCTION PROBLEM WITH A MOVING HEAT SOURCE

A numerical study of transient three-dimensional heat conduction problem with a moving source is presented. For numerical solution Douglas-Gunn alternating direction implicit method is applied and for the moving heat source flux distribution Gaussian function is used. An influence on numerical solution of input parameters figuring in flux boundary conditions is examined. This include parameters appearing in Gaussian function and heat transfer coefficient from free convection boundaries. Sensitivity of cooling time from 800 to 500 °C with respect to input parameters is also tested

Humerus absorbed dose in breast cancer postoperative radiotherapy. Simulation with FOTELP-VOX code and comparison with treatment planning system

Determining the dose of scattered radiation absorbed by specific body organs and tissues in radiotherapy is very important. In this study, we chose the humerus to determine the absorbed dose in female breast cancer patients who have undergone postoperative radiotherapy. In addition to direct dosimetry, another way to determine the absorbed dose to an identified organ of the human body is the FOTELP-VOX simulation. Selected five patients were treated at the Centre for Radiation Oncology, University Clinical Center Kragujevac during 2021. All plans were done on the treatment planning system ECLIPSE-Version 15.6 (Varian). Treatment has been performed using the 3D-CRT technique. The results of the comparison of the calculated dose in the tumor and humerus using simulations show that the bulk dose to the humerus did not exceed the set expected maximums. However, clinicians need to be aware of the risk in order to expose the humerus as little as possible. The FOTELP-VOX code, a modification of the general-purpose FOTELP code, used in this study has proven to be a valid practical way to perform accurate calculations of three-dimensional dose distribution from the interactions of particles in a complex target

Influence of pin geometry on mechanical and structural properties of butt friction stir welded 2024-T351 aluminum alloy

The aim of this work was to investigate the combined effect of small difference in pin geometry, together with rotation and welding speed on the weldability, mechanical and structural properties of FSW 2024-T351 Al plates. The only difference in tool pin design was the shape of thread: regular and rounded. Specimens were welded using rotation rate of 750 rev/min and welding speeds of 73 and 93 mm/min. In all four cases, specimens were defect free, with good or acceptable weld surface. Modification in pin design showed strong influence on macro structure and hardness distribution. Weak places are identified as low hardness zone, close to the nugget zone and are in good agreement with fracture location in tensile testing. Weld efficiency, as a measure of weld quality, are better in case of 310 tool, while UTS values can differ up to 13% for the equal welding parameters. Therefore, it can be assumed that small modification in tool design, particularly in pin geometry, can have great influence on weld formation and mechanical properties

NON-LINEAR TRANSIENT HEAT CONDUCTION ANALYSIS OF INSULATION WALL OF TANK FOR TRANSPORTATION OF LIQUID ALUMINUM

This paper deals with transient nonlinear heat conduction through the insulation wall of the tank for transportation of liquid aluminum. Tanks designed for this purpose must satisfy certain requirements regarding temperature of loading and unloading, during transport. Basic theoretical equations are presented, which describe the problem of heat conduction finite element (FE) analysis, starting from the differential equation of energy balance, taking into account the initial and boundary conditions of the problem. General 3D problem for heat conduction is considered, from which solutions for two- and one-dimensional heat conduction can be obtained, as special cases. Forming of the finite element matrices using Galerkin method is briefly described. The procedure for solving equations of energy balance is discussed, by methods of resolving iterative processes of nonlinear transient heat conduction. Solution of this problem illustrates possibilities of PAK-T software package, such as materials properties, given as tabular data, or analytical functions. Software also offers the possibility to solve nonlinear and transient problems with incremental methods. Obtained results for different thicknesses of the tank wall insulation materials enable its comparison in regards to given condition