Research on constitutive model of rheological behavior of 7050 aluminum alloy based on metal material of badminton racket frame

In order to improve people ‘s experience of badminton and improve the performance of badminton rackets. The flow stress behavior of 7050 aluminum alloy for badminton racket frame metal material was studied under the conditions of strain rate range of 0,01 ~ 10 s–1 and deformation temperature of 573 ~ 723 K. The true stress-strain curve of 7050 aluminum alloy was obtained. According to the real stress-strain curve, the Arrhenius constitutive model of 7050 aluminum alloy was constructed. The results show that obvious dynamic recovery and dynamic recrystallization occur in the hot compression deformation of 7050 aluminum alloy. The flow stress increases with the increase of strain rate and decreases with the increase of temperature. The theoretical stress value predicted by the constitutive model is fitted with the experimental value, and the correlation is 97,3 %. The constitutive model has high prediction accuracy

Microstructure and hardness of extrusion welding on hollow panel AA6061 aluminum alloy

Given the length of the structure, extruded products are occasionally joined to reach the desired length. To minimize production costs, this joint is achieved through extrusion welding, where it takes place while the workpiece is still a heated billet inside a chamber. As extrusion structures differ in complexity, this study seeks to identify the traits of extrusion welding outcomes across various structural designs. Research findings suggest that structural design significantly impacts both the physical and mechanical properties of the extruded plate and the extrusion joints

Effect of quenching temperature on microstructure and properties of 0Cr13Ni8Mo2Al stainless steel for piano stringer

T Stainless steel, as a common material for piano stringer, has the advantages of high strength and good toughness. 0Cr13Ni8Mo2Al stainless steel meets the strength and enhances the toughness of the piano string machine, so it is a relatively successful golf club material. A new type of 0Cr13Ni8Mo2Al stainless steel was studied. The microstructure, hardness and tensile properties of the stainless steel after quenching treatment were studied. The effects of quenching treatment on the microstructure, hardness, strength, plasticity and toughness of the alloy were clarified. The experimental results show that the best quenching process of stainless steel is 515 °C, the hardness is the highest 45.7 HRC, the tensile strength is the highest 145 MPa and the elongation is 13.8 %. This study has a certain guiding role in the development of piano stringing machine materials

Oksidacijsko-antioksidacijski procesi i toplinski učinci na oksidativni stres u gmazova

Temperature is the most important abiotic factor and has a direct influence on the physiology of the organism, affecting nearly all other parameters of the living environment of organisms. Ectothermic organisms are highly endangered in the current crisis climate, as they are unable to use metabolic heat to maintain body temperature. Reptiles are ectothermic vertebrates that are also susceptible to temperature fluctuations. Metabolism, muscle and nervous system function and reproduction are closely linked to reptile body temperature. To study the effects of temperature on oxidative stress, it is necessary to describe the generation of reactive oxygen species (ROS) and how organisms can prevent oxidative stress. This article describes the oxidation-antioxidation processes and the oxidative stress caused by thermal effects in reptiles. In the metabolic processes of aerobic organisms, ROS are continuously generated as by-products of oxidation-reduction reactions and are not primarily harmful. Furthermore, ROS are essential for many physiological functions, e.g., for energy production and for processes in the immune system. The potential toxicity of reactive oxygen radicals under physiological conditions is prevented by the antioxidant defence system. Oxidative stress occurs when the balance between oxidation and antioxidation systems is disturbed by excessive amounts of ROS or by the depletion of antioxidants. It is known that the metabolic rate of reptiles correlates with environmental temperature, making them physiologically more sensitive to temperature fluctuations compared to mammals. However, it must be considered that ectothermic organisms have evolved many thermal adaptations through physiological and behavioural measures to mitigate the resulting oxidative stress. However, further research in the fields of ecology, biogeography and evolution is needed to determine the exact effects of temperature on oxidative stress and the resulting changes in life characteristics in wild populations.Temperatura je glavni abiotički čimbenik i ima izravan utjecaj na fiziologške procese organizma. Nadalje, temperatura utječe na gotovo sve ostale okolišne čimbenike koji utječu na žive organizme. Predviđa se da će ektotermni organizmi zbog klimatskih promjena biti izloženi velikom riziku zbog njihove ovisnosti o temperaturi okoliša za održavanje tjelesne temperature. Gmazovi su ektotermni kralješnjaci, koji su kao i ostali ektotermni organizmi osjetljivi na temperaturne promjene. Metabolizam, rad mišića i živčanog sustava te reprodukcija ovisni su o tjelesnoj temperaturi gmazova. Za razumijevanje utjecaja temperature na oksidativni stres, nužno je razjasniti mehanizam nastanka reaktivnih kisikovih spojeva (ROS) te kako spriječiti nastanak oksidativnog stresa. U ovom radu opisat će se oksidacijsko-antioksidacijski procesi i oksidativni stres uzrokovan toplinskim učincima u gmazova. U metaboličkim procesima aerobnih organizama, ROS se kontinuirano stvaraju kao nusproizvodi oksidacijsko-redukcijskih reakcija te primarno nisu štetni. Štoviše, ROS su neophodni za brojne fiziološke funkcije, primjerice za proizvodnju energije i procese imunološkog sustava. Potencijalni štetni učinak reaktivnih kisikovih radikala/spojeva u fiziološkim uvjetima sprječava antioksidativni zaštitni sustav. Oksidativni stres nastaje kada je ravnoteža između oksidacijskog i antioksidativnog sustava poremećena zbog prekomjerne razine ROS-a ili smanjenja antioksidansa. Poznato je da je brzina metabolizma gmazova u korelaciji s temperaturom okoliša, što ih čini fiziološki osjetljivijima na promjene temperature u usporedbi sa sisavcima. No, potrebno je uzeti u obzir da su ektotermni organizmi razvili niz prilagodbi na promjenu temperature, putem fizioloških i bihevioralnih mehanizama te time ublažili nastali oksidativni stres. Međutim, da bi se utvrdio stvarni učinak temperature na oksidativni stres i posljedične promjene životnih obilježja u divljih populacija, potrebna su dodatna istraživanja u područjima ekologije, biogeografije i evolucije

Biokemijske karakteristike E. coli izdvojene iz hrane životinjskog podrijetla

Food of animal origin is a potential source of pathogenic E. coli that are dangerous to humans. While most strains are intestinal commensals, some can cause intestinal and extraintestinal infections. Their pathogenicity is associated with the presence of virulence genes, phylo-group and, in some strains, biochemical characteristics. In this study, a total of 61 E. coli isolates from meat, minced meat, meat preparations and carcass swabs from different animal species were analysed. The biochemical properties of the strains were determined using VITEK2 system and the data was compared with the presence of virulence genes from previous studies. The results showed a correlation between the presence of the eae virulence gene and the alkalinization of succinate. In addition, the presence of the virulence gene cnf1 was correlated with the enzyme tyrosine arylamidase, though the correlation between biochemical characteristics and the presence of virulence genes is questionable due to the small sample size and more strains need to be tested for further conclusions. Although no significant correlations were found between biochemical characteristics and the presence of virulence genes, this study describes the diversity of E. coli in the Republic of Croatia. The collected data also reveal new insights into biochemical characteristics of E. coli isolated from domestic and wild animals in the Republic of Croatia.Hrana životinjskog podrijetla predstavlja čest izvor patogenih sojeva Escherichia coli opasnih za ljude. Iako su većina sojeva crijevni komenzali, neki od njih mogu prouzročiti crijevne (intestinalne) i izvancrijevne (ekstraintestinalne) infekcije. Njihova je patogenost kod pojedinih serovarova povezana s prisutnošću gena za čimbenike virulencije, pripadnošću filogrupi te s biokemijskim svojstvima. U ovom istraživanju pretražen je 61 izolat bakterije E. coli izdvojenih iz uzoraka mesa: mljevenog mesa, mesnih pripravaka i obrisaka trupova različitih vrsta životinja. Izolatima su određene biokemijske karakteristike VITEK2 sustavom, a podatci su uspoređeni s prisutnošću gena za čimbenike virulencije obrađenim u prijašnjem istraživanju. Rezultati prikazuju povezanost između prisustva eae gena i aktivnosti alkalinizacije sukcinata. Osim navedenog, uočena je povezanost između prisustva cnf1 gena i aktivnosti enzima arilamidaze prema tirozinu. S obzirom na mali broj ostvarenih rezultata, nejasna je povezanost između biokemijskih karakteristika i prisutnosti gena za čimbenike virulencije. Stoga su potrebna daljnja istraživanja s većim brojem izolata. Iako nisu uočene značajne poveznice između biokemijskih svojstava i prisutnosti gena za čimbenike virulencije, ovim radom prikazane su raznolikosti E. coli u prikupljene na području Republike Hrvatske, a prikupljeni podatci prikazuju nova saznanja o biokemijskim karakateristikama E. coli u domaćih i divljih životinja na području Republike Hrvatske

Effect of normalizing temperature on microstructure and mechanical properties of ductile iron for piano iron plate

Piano iron plate is one of the components that play a decisive role in the quality of piano. In this paper, the effects of normalizing temperature on the microstructure and mechanical properties of nodular cast iron for piano iron plate were studied by normalizing at different temperatures and tempering at the same temperature. The microstructure observation, tensile test and impact test were used to study the effect of normalizing temperature on the microstructure and mechanical properties. The results show that after normalizing at 840 ~ 1 040 °C and tempering at the same temperature, the microstructure of ductile iron is mainly pearlite. In the normalizing temperature range of 840 ~ 1 040 °C, with the increase of normalizing temperature, the impact toughness and elongation of ductile iron increase, while the tensile strength and Brinell hardness show the opposite trend. When the normalizing temperature is 930 °C, the comprehensive mechanical properties of ductile iron are the best. At this time, the tensile strength is 815 MPa, the Brinell hardness is 328 HBW, the elongation is 3,79 %, and the impact toughness is 3,04 J / cm2

Effect of the post weld heat treatment on the microstructure of the underwater wet welding SS400 steel

The effects of the post weld heat treatment (PWHT) on the microstructure and hardness of the underwater wet welding (UWW) SS400 steel have been evaluated. The UWW was performed using Shielded Metal Arc Welding (SMAW) in water depth of 5.0 m, while PWHT was carried out on underwater welded specimen with temperature of 660 oC for 75 minutes. The result showed that the PWHT caused increasing the grain size of the microstructure and decreasing in hardness

Effect of quenching temperature on microstructure and mechanical properties of 50CrVA spring steel for mountain bike shock absorber

In order to improve the quality of people ‘s cycling and improve the safety performance of mountain bikes. The effects of quenching temperature on the microstructure and mechanical properties of 50 CrVA spring steel for mountain bike shock absorber were studied by means of microstructure observation, tensile test and impact test. The results show that the microstructure of 50CrVA steel is tempered troostite after quenching at 860-940 °C and tempering at 450 °C. In the quenching temperature range of 860 ~ 940 °C, with the increase of quenching temperature, the yield strength, tensile strength and elongation of 50CrVA steel increase first and then decrease, and reach the maximum at 920 °C, while the impact energy shows the opposite trend. When the quenching temperature is 920 °C and the tempering temperature is 450 °C, the comprehensive mechanical properties of 50CrVA steel are the best. At this time, the yield strength is 1 419MPa, the tensile strength is 1 538MPa, the elongation is 12 %, and the impact energy is 20,2J

Rapid spread of the Mediterranean glycophyte Catapodium rigidum in Hungary

This paper discusses the spread of the Mediterranean plant Catapodium rigidum (L.) C.E. Hubb. in Hungary, which is found in the transition zone between the sub-Mediterranean and continental climatic zones of Central Europe. This alien species has been found at 12 new localities in Hungary in recent years. Some of these stands are located along main roads, while others are found in urban weed vegetation. The species was most likely introduced by increasing road traffic and tourism. Our preliminary findings suggest that the spread of the species is not concentrated along main roads due to its salt sensitivity. Instead, it is more likely to be found in xerothermic weed vegetation in urban areas where salting and winter de-icing are not applied

Klinička procjena učinkovitosti meloxiveta u kompleksnom liječenju mačaka s karcinomom mliječne žlijezde

This study presents the results of a clinical administration of meloxivet nonsteroidal anti-inflammatory treatment against the background of the docetaxel + cyclophosphamide regimen chemotherapy following bilateral mastectomy in cats with mammary gland carcinoma. The inclusion of meloxivet in complex chemotherapy against breast carcinomas bilateral mastectomy improved treatment results. In particular, survival was extended in the clinical stages: I and II - by 1.3 times, III - by 1.6 times, and the disease-free period was increased by 1.5, 1.4 and 1.9 times, respectively. Complex treatment of cats including non-steroidal anti- inflammatory therapy reduced the risk of disease progression depending on the clinical stage during the first six months after the end of the course. An increase in the number of patients with subsequent metastasis (after six to twelve months) was also noted. The use of meloxivet made it possible to avoid disease progression in cats up to three years of age, and to reduce its probability and delay the onset of metastasis in all age categories. The proposed scheme of treatment of cats with mammary gland carcinomas reduced side effects, indicating an insignificant risk of negative effects of long-term meloxivet use against the background of a 1.5- fold reduction in the frequency of recurrences in the surgical intervention area.Ovaj rad predstavlja rezultate kliničkog istraživanja metronomske uporabe meloxivet nesteroidnog protuupalnog lijeka u usporedbi s DC (docetaksel + ciklofosfamid) režimom polikemoterapije nakon bilateralne mastektomije u mačaka s karcinomom mliječne žlijezde. Uključivanje meloxivet nesteroidnog protuupalnog lijeka u metronomski režim u kompleksnoj kemoterapiji kod bilateralne mastektomije zbog karcinoma mliječne žljezde pouzdano omogućuje (Р<0,001) poboljšanje rezultata liječenja. Posebice, produljenje razdoblja preživljavanja u kliničkoj fazi T1 N0 M0 (s 25,6±2,2 na 32,7±2,5 mjeseci), T2 N0 M0 (s 16,8±1,7 na 22,4±1,3 mjeseca), T1-2 N1 M0 (s 12,9±0,9 na 17,2±1,0 mjesec) za 1,3 puta, III (T3 N0-1 M0) za 1,6 puta (s 8.3±1.4 na 13,1±1,5 mjeseci) i razdoblje bez bolesti za 1,5 (s 14,0±1,8 na 21,1±2,2 mjeseca), 1,4 (s 12,8±1,9 na 18,1±1,3 mjeseca), 1,9 (s 7,2±1,0 na 13,5±1,6 mjeseci), odnosno 1,9 puta (s 4,4±0,5 na 8,3±0,8 mjeseci). Kompleksno liječenje mačaka koje je uključivalo nesteroidnu protuupalnu terapiju, ovisno o kliničkoj fazi tijekom prvih šest mjeseci nakon završetka tretmana s 22,2-70,0 % na 12,5-33,3 % smanjilo je rizik od progresije bolesti. Istovremeno, zamijećen je povećani broj pacijenata u kojih su se metastaze pojavile kasnije (nakon šest do dvanaest mjeseci). Uporaba meloxivet nesteroidnog protuupalnog lijeka omogućila je izbjegavanje progresije bolesti u mačaka do tri godine starosti te smanjenje vjerojatnosti i odgodu nastanka metastaza u svim dobnim kategorijama. Predložena shema liječenja mačaka s karcinomima mliječne žlijezde omogućila je smanjenje razine nuspojava, pokazujući beznačajan rizik od negativnih nuspojava na tijelo zbog dugoročne uporabe meloxiveta u odnosu na smanjenje učestalosti ponavljanja u kirurškom interventnom području za 1,5 puta