Additive manufacturing (AM) technology refers to the process of producing 3D objects by adding material in successive layers. Fused deposition modeling (FDM) is one of the AM technologies where objects are built by adding layers of melted thermoplastic filament onto the printing surface. Mechanical properties of FDM printed part depend on many influencing factors such as material composition, extruding temperature, printing parameters and environment temperature. The aim of this study was to investigate consistency of mechanical properties of elements produced by FDM additive manufacturing technology. To do so, mechanical tensile and compression tests were conducted on ten samples using polylactic acid (PLA) and ten samples using acrylonitrile butadiene styrene (ABS) thermoplastic material. Tensile tests were conducted using Shimadzu Compact Tabletop Testing Machine EZ-LX and the compression tests were done using VEB ZDM 5/91 testing machine. The ultimate tensile strength, strain, Young modulus and compression yield strength values were analyzed. The ABS thermoplastic material showed greater consistency in mechanical properties during tensile tests. Tensile strength values for PLA material varied between samples thus showing greater inconsistency in repeatability of mechanical properties. Compression tests, on the other hand, showed that PLA samples had greater consistency in mechanical properties compared to ABS samples.
Farm breeding of cattle is organized so that the animals are kept in a controlled environment (an closed corner, feeding time, milking time, workers), where daily animal encounter with familiar sounds, smells, movements and equipment. Any positive or negative change of environment causes certain physiological reactions of cattle on it. Negative stimuli (relocation, new technological activities, unidentified sounds and people) disrupt the homeostasis of the animals and lead them into a state of stress. During stress in cattle appears central inhibition of milk ejection from the alveoli of the udder, causing its incomplete emptying which could lead to pathological changes. In stressful situation, there is a connection between nervous (SA system), endocrine (HPA-axis) and the immune system. Stimuli from the outside were obtained through sight, hearing, smell and touch, leading to nerve impulses which then activate the endocrine system (increased levels of cortisol, β-endorphin, adrenaline, and reducing levels of oxytocin in the blood), whose actions over a long time lead to decline in immune response and susceptibility to disease. Many studies suggest an association between central inhibition of milk ejection and stressful situations (first milking of primiparious cattle, environment changes), but the very principle of inhibition is not fully understood. Some studies indicate an association between endogenous opioids (β-endorphin) and catecholamines (adrenalin) in the central inhibition of milk ejection, however, there is still no clear evidence and there is still plenty to do in this area.
The effect of chemical weed control with reduced herbicide rates (pre-em., pre-em. + post-em., post-em.) on weed population density and maize yield was compared in three tillage systems (mouldboard, chisel, disk harrowing) for lessive pseudogleyic soil in north-eastern Croatia (1997Croatia ( -1999. These main weeds were present in all tillage variants:and Calystegia sepium (L.) R.Br. The density of all weeds was significantly affected by tillage and it ranged from 204 plants on untreated plots with mouldboard to 372 and 421 plants per m 2 with chisel ploughing and disk harrowing, respectively. In comparison with standard tank-mixture of atrazine herbicide (metolachlor 50% & atrazine 20%) at the recommended rate, atrazine-free herbicide combinations (metolachlor + 50% prosulfuron & 30% primisulfuron-methyl; sulcotrione + bromoxynil; thifensulfuron-methyl + nicosulfuron) showed a similar total efficacy of weed control (95-96%). Band spraying with standard treatment at a half-recommended rate combined with mechanical weed control brought a satisfactory total weed reduction (83-87%). The weed control methods had no effects on maize yields that were significantly affected by year and tillage. Compared to the highest yield with mouldboard ploughing (10.2 t/ha), average percent yield depressions with chisel ploughing and disk harrowing were 10 and 22%, respectively.
The modern equipment introduction into cow milking created technical possibilities for studying the milk flow curve and for using the results in cattle selection. In preventing mastitis, besides curing, other parameters of the milk flow curve could be used preventively. Research showed that cows that had the milk flow curve with a short duration of increasing flow rate (dIFR≤0.40 min) and a larger quotient between the peak and down phase (QPD>1.20) had also the least somatic cell count in milk (LSCC = 3.47, and 3.30 respectively). Such relation is favourable because increasing the relation, the duration of quick and uniform milking extends, and the duration of peak flow rate shortens. That also show correlation coefficients which were between the logarithmic somatic cell count in milk (LSCC) on one hand and the peak flow rate (dPFR), that means the quotient of peak and down phase (QPD) on the other hand negative (r= -0.25** and -0.27**). Breeding-selective procedures could create bull fathers and mothers with the most desirable milk flow curve and the duration of certain milking phases, whereby the somatic cell count in milk would be the least. Therefore it would be necessary to define desirable proportions of the milk flow curve with a special attention to the cow's health udder.
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