Occupation and land degradation due to mining works: Example of the 'Kolubara' mining basin

The subject of this scientific-research paper is the occupation and land degradation due to mining works in the 'Kolubara' mining basin. The aim of the research is to determine areas exposed to degradation and to display devastated areas along with the possibility of conditions' improvement through the revitalization of certain areas. Additionally, the aim would be the proposal of measures for solving other ecological problems, such as waste, tailings sites and activities to reduce the level of environmental pollution and to conduct the proper monitoring

UPRAVLJANJE NEKRETNINAMA U PODUZEĆIMA NA PODRUČJU REPUBLIKE HRVATSKE : Diplomski rad

U ovom radu su analizirani stavovi Hrvatskih poduzeća prema nekretninama te prakse u upravljanju i donošenju odluka vezanih za nekretnine. Cilj rada je bio utvrditi da li Hrvatska poduzeća prate trendove koji se javljaju u razvijenim zemljama svijeta ili ipak zaostajemo u upravljanju. Istraživanje je ukazalo na slabu i lošu razvijenost praksi i procedura pri upravljanju nekretninama, nisku razinu profesionalnosti te činjenicu da se većina odluka donosi bez detaljnog plana i analize te s puno improvizacije. Također je pokazana jaka preferencija ispitanika prema vlasništvu u odnosu na najam.The subject of this analysis was behaviour of companies which operate on Croatian market, to define their preferences and attitudes towards real estate, and decision making process when it comes to making decisions about real estate. Aim of this paper was to determine if Croatian companies follow the trends which are visible in highly developed countries. Research showed the lack of procedures and practices regarding real estate management and it also pointed out that majority of decisions are made without proper analysis. Also one of conslusions was that there is strong preference towards ownership, rather than leasing

Modelling of Dross Height in Plasma Jet Cutting Process of Aluminium Alloy 5083 Using Fuzzy Logic Technique

Dross height is an important cut quality characteristic in plasma jet cutting process. It can be defined as molten metal blown from the cutting zone and localized on the bottom of the metal sheet. In each plasma jet cutting process, it is important to obtain dross free cuts. Aluminium is as material very present in shipbuilding and metal industry and because of that very usually cut by plasma jet. Because of high heat and electrical conductivity of aluminium, plasma jet cutting is followed by insecurity about process parameters settings that lead to optimal cut quality characteristics. The aim of this paper is to develop a fuzzy logic model that predicts the influence of variable process parameters on dross height in plasma jet cutting of aluminium alloy 5083. Experiments were performed according to Taguchi L27 orthogonal array by varying cutting speed, arc current and cutting height as input process parameters. Fuzzy logic model was defined using Mamdani inference system. This model was used to investigate effects of variable process parameters on dross height response. In order to analyse interaction effects of plasma jet cutting process parameters on dross formation 3D surface and contour plots were generated. The analysis revealed that the cutting speed has the most significant effect followed by arc current and cutting height. Obtained results of this research indicate that artificial intelligence technique, fuzzy logic, can be effectively used for modelling and prediction of dross formation in plasma jet cutting process of aluminium alloy

Structural analysis of three-metal explosion joint: Zirconium-titanium-steel

The influence of applied explosion joining parameters on the structure and strength of three-metal joints: Zr-Ti-Steel is analyzed in this paper. Zirconium was explosively clad on steel over an inter-layer of titanium. Zirconium-titanium-steel joint is produced during simultaneous cladding operation using a single cladding shot and plan parallel joining scheme. The metallographic analysis of interfaces Zr/Ti and Ti/Steel structures and microhardness measuring are performed. Mechanical testing of bond strength is performed on both interfaces by shear strength examinations

Wear of Induction Cladded Coating in the Abrasive Mass at Various Speeds and Impact Angles

The wear of induction cladded coating during motion was investigated through the abrasive mass at a speed of 1.0 to 3.0 m/s and the impact angle of abrasive particles with a worn surface of 0° to 90°. Cladding was performed by using Ni-Cr-Si-B-Fe flame spraying powder. Experimental research was carried out by using the Response Surface Method (RSM) and Central Composite Design (CCD). Analysis of variance proved that both motion speed and impact angle had significant impact on the wear of coating, both individually and interactively. Motion speed had the greatest influence, and the interaction of speed and angle had the least influence. The wear rate increased along with the motion speed increase, and the influence of the impact angle depends on the wear speed. At a speed of 1 m/s, the wear increases along with the increase of angle from 0° to 45° and then continues to decrease up to the angle of 90°. At a speed of 2 m/s, the wear increases along with the angle increase from 0° to 30° and then continues to decrease up to the angle of 90°. At a speed of 3 m/s, the wear increases along with the angle increase from 0° to 20° and then decreases as the angle increases up to 90°. Based on the statistical data processing, this research developed the mathematical model of wear in the form of quadratic polynomial that describes the influences of input variables in individual and interactive form

The Influence of Gas Heating on Material Properties of P92 Steel During Boiler Tube Alignment

The pipes and the pipe walls are of the utmost importance to all power plant facilities. Under exploitation, they are subjected to effects of aggressive media, high temperature corrosion and possible mechanical damage. Consequently, special attention is paid to the control of material properties during the power plant construction in order to minimize the risk of flaws or failures. In this paper, the influence of gas heating on the structure and properties of P 92 martensite steel is examined, as occurring during tube alignment. The experiments have been performed on the polished and shot – blasted surfaces, and the obtained results have been compared with the values of specimens with the same surface treatment, but without heat treatment

The Influence of Water on the Properties of Polyester Laminates Made by Manual Air Extrusion

The mechanical properties of polyester composites reinforced by various combinations of glass fibre types were investigated. The samples were tested before and after the operation of the wet media in the salt chamber. Cross sections were recorded to determine the presence of cavities. It was concluded that the properties of composites depended not only on the number and type of reinforcement but also much more on the portion of cavities. It is concluded that the intermediate surface with a smaller portion of the cavities contributes to the compositions to be firmer and stiffer, but also fragile. As a result, the negative influence of water increases with the increase of porosity

UPRAVLJANJE NEKRETNINAMA U PODUZEĆIMA NA PODRUČJU REPUBLIKE HRVATSKE : Diplomski rad

U ovom radu su analizirani stavovi Hrvatskih poduzeća prema nekretninama te prakse u upravljanju i donošenju odluka vezanih za nekretnine. Cilj rada je bio utvrditi da li Hrvatska poduzeća prate trendove koji se javljaju u razvijenim zemljama svijeta ili ipak zaostajemo u upravljanju. Istraživanje je ukazalo na slabu i lošu razvijenost praksi i procedura pri upravljanju nekretninama, nisku razinu profesionalnosti te činjenicu da se većina odluka donosi bez detaljnog plana i analize te s puno improvizacije. Također je pokazana jaka preferencija ispitanika prema vlasništvu u odnosu na najam.The subject of this analysis was behaviour of companies which operate on Croatian market, to define their preferences and attitudes towards real estate, and decision making process when it comes to making decisions about real estate. Aim of this paper was to determine if Croatian companies follow the trends which are visible in highly developed countries. Research showed the lack of procedures and practices regarding real estate management and it also pointed out that majority of decisions are made without proper analysis. Also one of conslusions was that there is strong preference towards ownership, rather than leasing

Application and Upgrading of On-line Monitoring System for Measurement and Processing of Electric Signals at Arc Stud Welding Process

As the application of on-line monitoring system is shown to be a good solution during monitoring of main welding parameters at different welding processes, this paper describes application and upgrading of an on-line monitoring system developed at the Mechanical Engineering Faculty in Slavonski Brod. The experiment described in the paper shows application of an on-line monitoring system during welding of two types of studs with application of activating flux for ATIG process (VS-2E) on the base metal surface. Monitoring of the main welding parameters (welding current and voltage) was conducted during welding of studs usually used in steam boiler production (stud diameter: 10 mm), and welding voltage was monitored on the studs (shear stud) of 22 mm diameters used in bridge construction. The goal of monitoring and analysis of main welding parameters is to evaluate the connection of electric arc parameters variations with the presence of an activating flux

Utjecaj kvalitete pripreme površine osnovnog materijala na otpornost naštrcanog sloja radijalnom i aksijalnom smiku

For the purpose of this experiment, respective surfaces of 42CrMo4 base material specimens were prepared for spraying using different technologies: turning, cutting of radial notches and cutting of axial notches. Gas aided thermal spraying of wire material was performed, laying a first layer of a nickel aluminum compound and a final Chrome Molybdenum Steel coating. Metallographic structure analysis and hardness measurement suggested that surface preparation quality does not affect hardness of the sprayed layer, but its thickness. Using a suitable tool, specimens were examined on radial and axial shear and these results were compared to previous ones. It could be determined that the notch size significantly affects both the thickness of the intermediate layer and its even distribution around the edge of the notch. A smaller radial notch allows for a higher torque momentum at radial shear, whilst best overall properties are achieved with axial notches subjected to radial loads. Testing axial shear, the cutting power proved dependant of the depth of radial notches, where low depth was inherent with low shear resistance.Na ispitnim uzorcima osnovnog materijala 42CrMo4 izvršene su različite pripreme površine: tokarenjem, narezivanjem aksijalnih i narezivanjem radijalnih utora. Izvršeno je plinsko naštrcavanje žicom: međusloj nikl- aruminid i završnog sloja Cr-Mo čelik. Metalografskim pretragama strukture i kontrolom tvrdoća utvrđeno je da kvaliteta pripreme površine ne utječe značajno na tvrdoću ali utječe na postignutu debljinu sloja. Odgovarajućim alatom izvršena su ispitivanja uzoraka na radijalni i na aksijalni smik. Međusobnom usporedbom rezultata ovih mjerenja s rezultatima kontrole tvrdoće i metalografskim pretragama strukture dolazi se do zaključka da veličina utora značajno djeluje na debljinu podsloja a pogotovo na njegovu ravnomjerno naštrcavanje po obodu utora. Sitniji radijalni utor doprinosi povećanju momenta zakretanja pri radijalnom smiku, ali se najbolja svojstva postižu u uvjetima aksijalnih utora radijalno opterećenih. Pri ispitivanju na aksijalni smik sila odreza ovisi o dubini radijalnih utora pri čemu mala dubina utora daje i malu otpornost na smik