The influence of the carbon content on the machinability of sintered valve plates

The quality of processedsinteredvalveplatesdepends on variousfactorsderiving both from thecharacteristics ofthe rawmaterial and the grinding process.The change of valve plate’s materialis defined based on the requirementsto reducethe priceof the inputmaterial.This paperexamines the impact of the carbon content on themachinability ofsinteredvalve plates. In evaluation the highest level of attention has been given to parameters critical to quality (CTQ - critical to quality), and that using the Minitab statistic tools

Uvođenje tehnologije eksplozijskog platiranja u postupku izrade hidrauličkih cilindara

The microhardness, microstructure and bond strength of the interface of a bi-metallic joint on the cross-section of the testing hydraulic cylinder were investigated. Experimental findings of related to both method of cladding obtained with metallographic and mechanical investigations of the interface between the CuSn6 bronze and the TS5 (Č.1213) steel cylinder, are given.Istraživani su mikrotvrdoća, mikrostruktura i čvrstoća veze međupovršine bimetalnog spoja po poprečnom presjeku ispitivanog hidrauličnog cilindra. Na osnovi metalografskih i mehaničkih ispitivanja međupovršine između CuSn6 bronce i čeličnog cilindra TS5 (Č.1213) usporedno su prikazani odgovarajući rezultati ovih dviju tehnologija platiranja

Optimalni model metode konačnih elemenata (MKE) konstrukcije strijele plovnog bagera

This paper is presentation of the development of advanced approach for modeling and structural analysis of jib structure which is usually part of waterway bucket dredgers. Object of analysis is a jib structure which will be reconstructed for the excavation of grain material from a river bed. Main goal of paper is to proof benefits of enough sophisticated i.e. “optimal” FEM model for structural analysis of this type of structures in comparison with simple, but not adequate models. Proper stress state is emphasized as primary, but not only condition. It is necessary to reach serviceability and durability state, as well as affordable financial construction circumstances.Rad je kratki prikaz razvitka naprednog pristupa u modeliranju i strukturnoj analizi konstrukcije strijele, koja je uobičajeni dio plovnih bagera. Predmet analize je konstrukcija strijele bagera vedričara rekonstruisanog za iskop šljunka sa dna vodotoka. Cilj rada je da dokaže prednosti dovoljno sofi sticiranog tj. “optimalnog” MKE modela za analizu ovog tipa konstrukcija u odnosu na jednostavne, ali neodgovarajuće modele. Odgovarajuće naponsko stanje je istaknuto kao primarni, ali ne i jedini uvjet za rabljenje bagera. Potrebno je osigurati i odgovarajuće stanje upotrebljivosti i trajnosti, kao i povoljne ekonomske uvjete izrade konstrukcije

Antibacterial and antifungal activity of the liverwort (Ptilidium pulcherrimum) methanol extract

The antimicrobial activity of the methanol extract from the liverwort, Ptilidium pulcherrimum was evaluated against five bacterial and six fungal species. In vitro antibacterial activity was assessed by disc diffusion and microdilution methods. The extract showed a stronger effect against tested Gram (+) than Gram (-) bacteria. The antifungal activity of the methanol extract was tested using a microdilution method. The methanol extract showed strong antifungal activity. The best antifungal activity was achieved against Trichoderma viride compared to the synthetic fungicide bifonazol

Integrirana procjena MIG (Metal inertni plin) i MAG (Metal aktivni plin) procesa zavarivanja

Taking into account the technical characteristics of the welding processes, associated with the fulfilling clients’ requirements, the assurance of safe and healthy working places as well as the environment protection the fundamental meaning belongs to the application of the appropriate methods of risk assessment of these processes. The paper presents the results of risk analysis, using an integrated risk indicator implemented into operation of the MIG and MAG welding processes in the practice. In the welding risk management one can decide about reduce the risk by avoiding the risky ventures, or as a result of the proper preventive actions’ application.Uzimajući u obzir tehničke karakteristike postupaka zavarivanja, povezane sa ispunjenjem zahtjeva kupaca, osiguranja sigurnosti i zdravlja na radnim mjestima te zaštite okoliša, kao temeljni zahtjev pojavljuje se primjena odgovarajućih metoda procjene rizika tih procesa. U radu su dati rezultati provedene analize, korištenjem integriranog pokazatelja rizika u operacijama MIG i MAG zavarivanja u praksi. U upravljanju rizikom zavarivanja može se smanjiti rizik procesa ili izbjegavanjem rizičnih ulaganja u opremu ili kao rezultat uvođenja odgovarajućih preventivnih mjera

Risk based on quality, environmental and occupational safety in heat treatment processes

Growing competition on the market forces the organisations to be more technological and organisational flexibility, both in the range of ensuring the products’ quality and minimising the affect the surrounding environment as well as limiting the threats of the work safety. The studies proposed the way of consistent risk management of the operational discrepancies, based on the operational control, aiming at confirming the consistency of the key characteristics with the fixed operational criteria. The applied method guarantees avoiding the estimated risk, as unaccepted, and supervising and keeping on the even level the risk classified as the accepted one, which was used in the processes of the heat treatment

Investigation on antibacterial synergism of Origanum vulgare and Thymus vulgaris essential oils

Essential oils are well known as strong antimicrobial agents of plant origin. In spite of this, the antimicrobial synergism of essential oils isolated from different plant species is poorly investigated. The following study examines the synergism of the essential oils of Origanum vulgare L. and Thymus vulgaris L against pathogenic bacteria, Staphylococcus aureus and Salmonella typhimurium. First, the antibacterial effect of the oils was tested, and the minimal inhibitory concentrations (MIC) of both oils were determined using the microdilution method. To test whether the oils act synergistically, every possible combination of essential oil concentrations was used in a dynamic checkerboard method. The results indicated that the oils indeed acted synergistically with fractional inhibitory concentration indexes of 0.45 and 0.50. [Projekat Ministarstva nauke Republike Srbije, br. 173032

Antibacterial and antifungal activity of the liverwort (Ptilidium pulcherrimum) methanol extract

The antimicrobial activity of the methanol extract from the liverwort, Ptilidium pulcherrimum was evaluated against five bacterial and six fungal species. In vitro antibacterial activity was assessed by disc diffusion and microdilution methods. The extract showed a stronger effect against tested Gram (+) than Gram (-) bacteria. The antifungal activity of the methanol extract was tested using a microdilution method. The methanol extract showed strong antifungal activity. The best antifungal activity was achieved against Trichoderma viride compared to the synthetic fungicide bifonazol.Antibakterijsko i antifungalno dejsto metanolnog ekstrakta jetrenjače Ptilidium pulcherrimum ispitivano je na 5 vrsta bakterija i 6 mikromiceta. Za ispitivanje in vitro antimikrobnog dejstva ekstrakta korišćena je metoda mikrodilucije na mikrotitracionim pločama i metoda difuzije sa filter diskova. Ekstrakt je pokazao jači efekat na testirane Gram (+), nego na Gram (-) bakterije. Antifungalna aktivnost metanolnog ekstrakta ispitana je mikrodilucionom metodom. Testirani ekstrakt pokazao je jak antifungalni potencijal na Trichoderma viride, Bifonazol je pokazao skoro identičnu fungistatičku aktivnost, dok je njegova fungicidna aktivnost bila nešto viša u poređenju sa metanolnim ekstraktom analizirane jetrenjače.Projekat ministarstva br. 143049 i 14304

Hemijski sastav i antifungalna aktivnost etarskog ulja daglasove jele (Pseudosuga menziesii mirb. Franco) iz Srbije

The chemical composition of the essential oil of fresh young needles with twigs of Douglas fir (Pseudosuga menziesii Mirb. Franco) obtained by hydrodistillation were analyzed by gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS). Ten compounds, accounting for 94.26 % of the oil, were identified. The main compounds found were bornyl acetate (34.65 %), camphene (29.82 %), alpha-pinene (11.65 %) and santene (5.45 %). The antifiangal activity of the essential oil was tested against various fungal species. The minimum inhibitory concentration of Douglas fir essential oil ranged from 1.5 to 4 mu g mL(-1). The fungi most sensitive to the tested oil were Phomopsis helianthi, while Penicillium species, along with Microsporum canis, were the most resistant. Compared to the commercial fungicidal agent bifonazole, the studied essential oil demonstrated higher antifungal activity.Hemijski sastav etarskog ulja mladih iglica sa grančicama duglazije (Pseudosuga menziesii Mirb. Franco) dobijenog destilacijom vodenom parom, analiziran je gasnom hromatografijom (GC) i kombinacijom gasne hromatografije i masene spektrometrije (GC/MS). Identifikovano je deset jedinjenja ukupne zastupljenosti 94,26 %. Kao glavne komponente su nađeni: bornil-acetat (34,65 %), kamfen (29,82 %), α-pinen (11,65 %) i santen (5,45 %). Pored toga, etarsko ulje je testirano na antifungalnu aktivnost. Etarsko ulje pokazuje mnogo bolju antifugalnu akivnost od komercijalnog fungicidnog agensa bifonazola. Minimalna inhibitorna koncentracija etarskog ulja duglazije je u opsegu od 0,6 do 1,4 μL mL-1. Najosetljiviji na testirano ulje je bio soj Phomopsis helianthi, dok sojevi Penicillium i Microsporum canis pokazuju najveću rezistentnost