EXPERIMENTAL RESEARCH OF THE DUPLEX STAINLESS STEEL WELDS IN SHIPBUILDING

Duplex stainless steel is used in shipbuilding increasingly because of its good mechanical properties and marked corrosion resistance. This steel has a two phase structure (austenite-ferrite) which is sensitive on heat input during welding because of the possible ferritisation appearance, that is, increase in ferrite content in the area of heat effected zone (HAZ) which can lead to loss of mechanical and corrosion properties. Work with duplex stainless steel requires special attention in every phase of production process, from storage, material handling, up to welding and welded joint surface treatment, in order to achieve a high quality welded joint and assure long-lasting corrosion resistance of the structure. In the beginning, this paper explains basic characteristics of the duplex stainless steel. In the experimental part, macrostructure, microstructure and corrosion resistance testing of butt welds, fillet welds and welded studs were performed. Results of the research are a basis for conclusions and suggestions for successful applications of duplex stainless steel in shipbuilding

Propagacija nelinearnih pojava u mjernom nizu

Rezultat mjerenja je brojčana procjena mjerene veličine uz pridruženu kvantitativnu analizu vjerojatnosti. Mjerenja su propisane strukture upravo zato da omoguće istraživačima, stručnjacima i drugim mjeriteljima najveću moguću pouzdanost u rezultate. Na taj način, kao sljedeće svojstvo, vjerojatnost ostvarivanja nepredviđenih ili neželjenih posljedica je minimalna. Ipak, zbog relativno velikog broja stupnjeva slobode u tipičnom mjeriteljskom slijedu, njegovog nelinearnog karaktera i nelinearnih sprezanja, općenito nije poznato u kojem iznosu varijacija u uvjetima mjerenja dovodi do znatno veće varijacije u mjerenoj veličini ili njenim izvedenicama. U ovom radu razmatramo potankosti navedenog utjecaja varijacija i diskutiramo o mogućim rezultatima. Kao ilustraciju razmatranih utjecaja prikazujemo rezultate koji se odnose na relativno jednostavno i uobičajeno mjerenje površinske hrapavosti objekata u čvrstom stanju. Pokazano je kako nema znatnih povećanja varijacija u početnim parametrima duž mjerniteljskog niza

Utjecaj tehnoloških parametara na zaštitna svojstva vodorazrjedivih premaza

U današnje vrijeme korozijsko djelovanje je jedan od ključnih faktora u ekonomskom, sigurnosnom i ekološkom aspektu, čime je poraslo zanimanje za ovu problematiku i moguća rješenja smanjenja korozijskog djelovanja primjenom neke od metoda površinske zaštite. Negativna strana je ta što se postupci površinske zaštite provode primjenom tvari koje su nerijetko štetne za čovjeka i okoliš. Suvremena rješenja su ekološki prihvatljivi vodorazrjedivi premazi za zaštitu od korozije. Njihov razvoj i sve veća primjena posebno su intenzivirani zbog zakonskih odredbi koje ograničavaju emisiju hlapivih organskih otapala u okoliš. Ipak, šira primjena je još uvijek izostala, a prvenstveno zbog, u prošlosti slabijih, a danas nedovoljno poznatih zaštitnih karakteristika. Za uvođenje i širu primjenu vodorazrjedivih premaza ključno je što bolje poznavanje njihovih zaštitnih svojstava i ograničenja u primjeni, čime bi se osigurala zaštita od korozije bez pojave grešaka. U cilju proširenja dosadašnjih saznanja, u doktorskom radu su istražena svojstva i ponašanje vodorazrjedivih premaza kod različitih temperatura sušenja, kod nanošenja u debelom sloju te je posebno istražena učinkovitost zaštite vodorazrjedivim sustavima premaza. Kako bi se rezultati istraživanja vodorazrjedivih premaza lakše interpretirali, istraživanja su usporedno provedena i na premazima na bazi otapala koji se danas uspješno primjenjuju za zaštitu od korozije. Za istraživanja su korištene znanstvene polarizacijske elektrokemijske metode, ispitivanja elektrokemijskom impedancijskom spektroskopijom te ubrzana korozijska ispitivanja u komorama. Učinkovitost sustava premaza na djelovanje primorske atmosfere u uvjetima cikličkog močenja površine je ispitana naizmjeničnim uranjanjem. Sušenje premaza je istraženo periodičkim praćenjem tvrdoće i drugih fizikalnih svojstva premaza te mjerenjem vremena sušenja uređajem „drying recorder“. Svojstva sloja kod različitih temperatura sušenja te nanošenja u debelom sloju su promatrana na pretražnom elektronskom mikroskopu. \Nakon izučavanja literature, završetka svih predviđenih ispitivanja, te analize rezultata i rasprave dat je zaključak istraživanja. Rezultati istraživanja predstavljaju doprinos u poznavanju zaštitnih svojstva i mehanizma otvrdnjavanja vodorazrjedivih premaza kod različitih uvjeta sušenja te se mogu izravno primijeniti kao smjernice za pravilnu uporabu vodorazrjedivih premaza, a kako bi se ostvarila potrebna kvaliteta zaštite od korozije uz smanjenje štetnog utjecaja na radnu okolinu

Zbornik radova 19. Savjetovanja o zaštiti materijala i industrijskom finišu (KORMAT 2010)

Zbornik radova Međunarodnog savjetovanja o zaštiti materijala i industrijskom finišu KORMAT 2010 održanog u Zagrebu 15.04.2010. na Zagrebačkom velesajmu

Propagation of Nonlinear Phenomena in a Measurement Sequence

Measurements provide one with results, in the form of both quantitative estimates of measured quantity along with attributed quantitative probabilistic analysis. Measurement is prescribed precisely in order to enable researchers, experts or other measurers to obtain maximum confidence in its results. In that way, the probability of obtaining unpredicted or unwanted consequences is minimised. Yet, owing to a rather large number of degrees of freedom in a typical measurement sequence, its nonlinear character and nonlinear couplings, in general it is not known in what amount a variation in measurement conditions brings about significantly larger variations in measured quantities or its derivatives. In this article we treat in some details the aforementioned influence of variations and argue about possible results. In order to illustrate the treated influences we present results of a rather simple and common measurement of surface roughness of solid state objects. It is argued that there is no significant augmentation of variations in results of initial measurements throughout measurement sequence

Corrosion inhibition of carbon steel in saline solutions by gluconate, zinc sulphate and green clay eluate

U ovom je radu procijenjen utjecaj glukonata, cink sulfata i eluata zelene gline na inhibiciju korozije ugljičnog čelika (EN S235 JRG) u 0,5 % i 3,5 % otopini natrij klorida pomoću metode Tafelove polarizacije. Primjenom umjerenih koncentracija natrij glukonata postignuta je značajna inhibicija opće korozije. U tom je slučaju inhibicija uglavnom ostvarena anodnim mehanizmom inhibicije opće korozije, uz pojavu lokalne "pitting" korozije ugljičnog čelika. Međutim, u slučaju kada je natrij glukonat pomiješan s cinkovim sulfatom i/ili eluatom zelene gline u odgovarajućim koncentracijama, dolazi do smanjenja i opće i lokalne korozije što ukazuje na dobro sinergijsko djelovanje između uporabljenih inhibitora.The effect of gluconate, zinc sulphate and green clay eluate on the corrosion inhibition of carbon steel (EN S235 JRG) in 0,5 % and 3,5 % sodium chloride solution has been evaluated in this work using Tafel polarization technique. Substantial general corrosion inhibition using sodium gluconate solely can be obtained with moderate concentrations. In this case, corrosion inhibition is predominately obtained by anodic mechanism and is limited to general corrosion, whereas carbon steel becomes liable to localised pitting corrosion. However, when sodium gluconate is combined with zinc sulphate and/or green clay eluate in adequate concentrations both general and localized corrosion are diminished which indicates good synergy between applied inhibitors

COMPARATIVE REVIEW OF GINGIVAL RETRACTION AGENTS

In order to obtain an adequate impression of demarcation line area of a prepared tooth located in or below the gingival edge it is necessary to perform the dilatation and drying of the gingival sulcus using retraction cord impregnated with adequate retraction agents. The aim of the study was to carry out comparative analysis of advantages and disadvantages of commercially available gingival retraction agents. Commercial retraction agents include astringents (metal salts) and vasoconstrictors on the basis of epinephrine. Further research should be aimed at examining the possibility of using sympathomimetic vasoconstrictors (tetrahydrosolin and oxymetasolin) for gingival retraction

Uticaj različitih načina pranja okrvavljene tkanine na ekspertizu tragova krvnih mrlja i rezultat DNK analize

In practice, there are often various attempts to remove traces of blood from items in order to conceal a crime. In the study, samples of bleached cotton fabric (360 samples in total) were used, which were then washed through one of six different washing cycles. After a period of time the samples were analyzed. The macroscopic appearance of the samples, the reaction of the samples to chemical tests for the presence of blood, quantity (concentration) of DNA, DNA degradation index and DNA profiles were analyzed. Machine washing at a temperature of 95 and 60oC using detergent can remove visible but not invisible traces of bloodstains up to 10 days old, while bloodstains aged 30 days cannot be removed in one washing cycle. Regardless of the method of washing, after washing, the visible remaining part of the bloodstain will be the dominant circumferential edge of the area of the original bloodstain. Comparative analysis with the results of DNA analysis revealed that washing older bloodstains from the cotton fabric makes it easier to remove the DNA, while the visual feature of bloodstains originating from hemoglobin is more difficult to remove in older bloodstains. The statistical significance of the DNA degradation index of the material remaining in the bloodstains after washing was revealed at the same time concerning the washing temperature (95 and 60oC) and the application of the detergent, with the existence of a synergistic enhancing effect of these two factors on the DNA degradation index. This pattern is completely absent in the sample group washed at 30oC. By comparing the results, it was concluded that different experimental conditions in this study, namely water temperature and detergent, affect different target parts of DNA (different STR loci) and thus accelerate the degradation of DNA. Therefore, early-stage DNA degradation does not occur uniformly in all parts of the genetic material, but this effect is lost with the passage of time and degradation becomes more alike in all parts of the DNA. This research identifies certain new scientific facts that provide forensic experts with a new perspective on concealing the traces of crime

Octreotide in the therapy of recurrent medulloblastomas

BACKGROUND: Recurrence of medulloblastoma appears after 30% to 40% of the surgeries. Different from primary medulloblastoma, in which five-year survival rate is 50%, the survival time of relapses much shorter and only 20% of the patients manage to survive a year. There is a logical need for additional methods of treatment of recurrent medulloblastomas. The aim of the study is to determine the effects of intracavitary and long-term subcutaneous application of Sandostatin (octreotide) on the recurrent medulloblastomas. METHODS: Fourteen children aged 4 to 9 years, in which, despite of craniospinal irradiation and chemotherapy came to a recurrence of medulloblastoma during the first 6 months after the surgery, were treated subcutaneously with Sandostatin (octreotide) in a longer period of time. Cerebellar medulloblastomas with a diameter bigger than 20 mm and spinal over 10 mm were removed operatively and octreotide with Beriplast was applied intracavitary. RESULTS: Magnetic resonance of cranioaxis shows that the application of octreotide has caused the disappearance of spinal drop metastases in all 7 patients and the cerebellar metastases smaller than 5 mm in all 4 patients. Subcutaneous application of octreotide combined with intracavitary expresses an antitumoral effect in 2/3 of the relapses. The application of octreotide results with a transformation of Chang's stage M0 into M1 in 71.43% of the patients. CONCLUSION: In the case of in loco or metastatic recurrence of medulloblastomas, intracavitarily and subcutaneously applied octreotide results with a regression of the tumor in a 3 year time within 2/3 of the treated patients