Superação da dormência em sementes de Murdannia nudiflora (L.) Brenan

The objective of this study was to identify treatments capable of promoting and standardizing the germination of Murdannia nudiflora (L.) Brenan seeds. The seeds of this weed were submitted to the following treatments: mechanical abrasion with 220-grit sandpaper (20, 30 and 40 frictions); immersion in sulfuric acid (90% for 30 and 40 seconds), followed by washing in running water; immersion in sodium hypochlorite (2.5% for 8 and 12 hours) and lye (5 minutes), followed by five washings in distilled water; immersion in KNO 3 (1% for 24 hours); preheating at 40°C in a humid or dry substrate for 2, 3 and 4 weeks. The statistical design was totally randomized, with four repetitions. The number of germinated seeds was counted every other day. The most favorable treatments were preheating at 40°C in humid substrate for 3 weeks, followed by mechanical abrasion after 40 frictions and immersion in sulfuric acid for 40 seconds.

Efeito da temperatura de pré-aquecimento e características do pulso na microestrutura de aço estrutural de alta resistência e baixa liga soldado com arco elétrico e proteção gasosa

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Avaliação das propriedades mecânicas e da microestrutura de aços dissimilares ABNT 8620 e ABNT 6655 LN 28 soldados com arco pulsado com diferentes temperaturas de pré-aquecimento e tipos de tecimento

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Análise do escoamento turbulento por um queimador industrial a gás utilizando dinâmica dos fluidos computacional

Pós-graduação em Engenharia Mecânica - FEG

Numerical modeling of flow through an industrial burner orifice

This paper presents numerical modeling of a turbulent natural gas flow through a non-premixed industrial burner of a slab reheating furnace. The furnace is equipped with diffusion side swirl burners capable of utilizing natural gas or coke oven gas alternatively through the same nozzles. The study is focused on one of the burners of the preheating zone. Computational Fluid Dynamics simulation has been used to predict the burner orifice turbulent flow. Flow rate and pressure at burner upstream were validated by experimental measurements. The outcomes of the numerical modeling are analyzed for the different turbulence models in terms of pressure drop, velocity profiles, and orifice discharge coefficient. The standard, RNG, and Realizable k-epsilon models and Reynolds Stress Model (RSM) have been used. The main purpose of the numerical investigation is to determine the turbulence model that more consistently reproduces the experimental results of the flow through an industrial non-premixed burner orifice. The comparisons between simulations indicate that all the models tested satisfactorily and represent the experimental conditions. However, the Realizable k-epsilon model seems to be the most appropriate turbulence model, since it provides results that are quite similar to the RSM and RNG k-epsilon models, requiring only slightly more computational power than the standard k-epsilon model. (C) 2014 Elsevier Ltd. All rights reserved.

Desenvolvimento de estrutura para purificação de água potável, através da irradiação de UV com lâmpadas fluorescentes especiais

Pós-graduação em Engenharia Elétrica - FEIS

A influência da temperatura de pré-aquecimento e tecimento na microestrutura e propriedades mecânicas na soldagem MIG/MAG robotizada de aços SAE 8620 com ABNT LN28

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Desenvolvimento de uma câmara para combustão de combustíveis líquidos, operando sob regime de combustão sem chama visível

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Ultrafeine Aerosolpartikel in der Stratosphäre

Ein neu konstruierter Kondensationskernzähler COPAS (COndensation PArticle counting System) für in-situ-Messungen der Konzentration von Aitken-Teilchen und ultrafeinen Aerosolpartikeln wurde im Rahmen dieser Arbeit erstmals erfolgreich bei Flugzeugmessungen eingesetzt. COPAS ist ein für flugzeuggestützte Messungen an Bord des Forschungsflugzeuges „Geophysica“ in der oberen Troposphäre und unteren Stratosphäre angepaßtes und voll automatisiertes System. Die Verfahrensweise, die Aerosolpartikel des Größenbereichs mit Durchmessern d < 100 nm zum Anwachsen zu bringen, um sie mittels optischer Detektion zu erfassen, ist im COPAS durch das Prinzip der thermischen Diffusion realisiert, wodurch eine kontinuierliche Messung der Aerosolkonzentration mit der untersten Nachweisgrenze für Partikeldurchmesser von d = 6 nm gewährleistet ist. Durch die Verwendung einer Aerosolheizung ist die Unterscheidung von volatilem und nichtvolatilem Anteil des Aerosols mit COPAS möglich. In umfassenden Laborversuchen wurde das COPAS-System hinsichtlich der unteren Nachweisgrenze in Abhängigkeit von der Betriebstemperatur und bei verschiedenen Druckbedingungen charakterisiert sowie die Effizienz der Aerosolheizung bestimmt. Flugzeuggestützte Messungen fanden in mittleren und polaren Breiten im Rahmen des EUPLEX-/ENVISAT-Validierungs–Projektes und in den Tropen während der TROCCINOX/ENVISAT-Kampagne statt. Die Messungen der vertikalen Konzentrationsverteilung des Aerosols ergaben in polaren Breiten eine Zunahme der Konzentration oberhalb von 17 km innerhalb des polaren Vortex mit hohem Anteil nichtvolatiler Partikel von bis zu 70 %. Als Ursache hierfür wird der Eintrag von meteoritischen Rauchpartikeln aus der Mesosphäre in die obere und mittlere Stratosphäre des Vortex angesehen. Ferner konnte in der unteren Stratosphäre des polaren Vortex der Einfluß troposphärischer Luft aus niedrigen Breiten festgestellt werden, die sich in einer hohen Variabilität der Aerosolpartikelkonzentration manifestiert. In tropischen Breiten wurde die Tropopausenregion untersucht. Dabei wurden Konzentrationen von bis zu 104 ultrafeiner Aerosolpartikel mit 6 nm < d < 14 nm pro cm-3 Luft gemessen, deren hoher volatiler Anteil einen sicheren Hinweis darauf gibt, daß die Partikel durch den Prozeß der homogenen Nukleation gebildet wurden. Damit konnte erstmals die Schlußfolgerungen von Brock et al. (1995) durch direkte Messungen der ultrafeinen Partikelkonzentration weitergehend belegt werden, daß in der tropischen Tropopausenregion die Neubildung von Aerosolpartikeln durch homogene Nukleation stattfindet. Die vertikalen Verteilungen der stratosphärischen Aerosolpartikelkonzentration mittlerer Breiten verdeutlichen die Ausbildung einer über 6 Jahre hinweg nahezu konstanten Hintergrundkonzentration des stratosphärischen Aerosols unter vulkanisch unbeeinflußten Bedingungen. Ferner gibt die vergleichende Untersuchung der stratosphärischen Aerosolpartikelkonzentration aus polaren, mittleren und tropischen Breiten Aufschluß über den Transport und die Prozessierung des stratosphärischen Aerosols und insbesondere über den Austausch von Luftmassen zwischen der Stratosphäre und der Troposphäre.

Addition of Zinc Sulfide Shells to Semiconducting Nanoparticles and its Effect on the Nanoparticle Fluorescence Emission Properties

The addition of a ZnS shell to CdSe and CdS quantum dot cores was explored using various methods. Spectrophotometry was used to assess the success of ZnS overcoating, which produces both an increase in overall fluorescence and decrease in particle size distribution. A new method was developed, involving preheating of the zinc and sulfide precursor solutions, resulting in CdSe(ZnS) particles with improved fluorescence and a more uniform shell coating from oleylamine-capped CdSe core particles.

Untersuchung zur Reduzierung des Verzugs durch Vorwärmung bei der Herstellung von Aluminiumbauteilen mittels SLM

Das generative Fertigungsverfahren Selective Laser Melting (SLM) wird zur direkten Herstellung von metallischen Funktionsbauteilen verwendet. Während des Bauprozesses entstehen durch den schichtweisen Aufbau und die lokale Energieeinbringung mittels eines fokussierten Laserstrahls thermisch induzierte Eigenspannungen, die zu Verzug des Bauteils oder von Bauteilbereichen führen können. Üblicherweise werden die Verzüge durch Stützstrukturen zwischen Bauteil und Substratplatte verhindert. Jedoch ist es nicht immer möglich alle Bereiche eines Bauteils, je nach Komplexität der Geometrie oder Zugänglichkeit, mit Stützstrukturen zu versehen bzw. diese wieder zu entfernen. Durch eine Vorwärmung der Substratplatte während des Bauprozesses können die Verzüge reduziert oder ganz vermieden werden. Jedoch ist bisher keine systematische Untersuchung des Einflusses der Vorwärmung auf Verzüge von Aluminium Bauteilen durchgeführt worden. Ziel dieser Arbeiten ist daher die systematische Untersuchung der Auswirkung einer Vorwärmung beim SLM von Aluminiumbauteilen und die Ermittlung der geeigneten Vorwärmtemperatur, bei der nahezu keine Verzüge mehr entstehen. Eine signifikante Verzugsreduzierung im Vergleich zu den Verzügen ohne Vorwärmung zeigt sich ab einer Vorwärmtemperatur von 150°C. Bei einer Vorwärmtemperatur von 250°C sind im Rahmen der Messgenauigkeit unabhängig von der untersuchten Twincantilever Testgeometrie keine Verzüge mehr feststellbar. Neben der Reduzierung der Verzüge verhindert die Vorwärmung außerdem spannungsbedingte Risse im Bauteil, die ohne Vorwärmung zum Abreißen von Teilen der Testgeometrie führen können. Mit 90 HV 0,1 bei 250°C Vorwärmtemperatur ist die Härte größer als die geforderte Mindesthärte nach DIN EN 1706 von Druckgussbauteilen aus dem Werkstoff AlSi10Mg. Aus diesem Ergebnis kann abgeleitet werden, dass eine Vorwärmtemperatur von 250°C geeignet ist, Bauteile aus dem Werkstoff AlSi10Mg mit SLM defektfrei und prozesssicher herzustellen und Verzüge vollständig zu vermeiden.

In vitro precision of fit of computer-aided designed and computer-aided manufactured titanium screw-retained fixed dental prostheses before and after ceramic veneering

OBJECTIVE To compare the precision of fit of full-arch implant-supported screw-retained computer-aided designed and computer-aided manufactured (CAD/CAM) titanium-fixed dental prostheses (FDP) before and after veneering. The null-hypothesis was that there is no difference in vertical microgap values between pure titanium frameworks and FDPs after porcelain firing. MATERIALS AND METHODS Five CAD/CAM titanium grade IV frameworks for a screw-retained 10-unit implant-supported reconstruction on six implants (FDI tooth positions 15, 13, 11, 21, 23, 25) were fabricated after digitizing the implant platforms and the cuspid-supporting framework resin pattern with a laser scanner (CARES(®) Scan CS2; Institut Straumann AG, Basel, Switzerland). A bonder, an opaquer, three layers of porcelain, and one layer of glaze were applied (Vita Titankeramik) and fired according to the manufacturer's preheating and fire cycle instructions at 400-800°C. The one-screw test (implant 25 screw-retained) was applied before and after veneering of the FDPs to assess the vertical microgap between implant and framework platform with a scanning electron microscope. The mean microgap was calculated from interproximal and buccal values. Statistical comparison was performed with non-parametric tests. RESULTS All vertical microgaps were clinically acceptable with values <90 μm. No statistically significant pairwise difference (P = 0.98) was observed between the relative effects of vertical microgap of unveneered (median 19 μm; 95% CI 13-35 μm) and veneered FDPs (20 μm; 13-31 μm), providing support for the null-hypothesis. Analysis within the groups showed significantly different values between the five implants of the FDPs before (P = 0.044) and after veneering (P = 0.020), while a monotonous trend of increasing values from implant 23 (closest position to screw-retained implant 25) to 15 (most distant implant) could not be observed (P = 0.169, P = 0.270). CONCLUSIONS Full-arch CAD/CAM titanium screw-retained frameworks have a high accuracy. Porcelain firing procedure had no impact on the precision of fit of the final FDPs. All implant microgap measurements of each FDP showed clinically acceptable vertical misfit values before and after veneering. Thus, the results do not only show accurate performance of the milling and firing but show also a reproducible scanning and designing process.

Geochemical analysis of minerals from sediment core CRP-2 in the Ross Sea, Antarctica

Distribution patterns, petrography, whole-rock and mineral chemistry, and shape and fabric data are described for the most representative basement lithologies occurring as clasts (granule to bolder grain-size class) from the 625 m deep CRP-2/2A drillcore. A major change in the distribution pattern of the clast types occurs at c. 310 mbsf., with granitoid-dominated clasts above and mainly dolerite clasts below; moreover, compositional and modal data suggest a further division into seven main detrital assemblages or petrofacies. In spite of this variability, most granitoid pebbles consist of either pink or grey biotite±hornblende monzogranites. Other less common and ubiquitous lithologies include biotite syenogranite, biotite-hornblende granodiorite, tonalite, monzogranitic porphyries (very common below 310 mbsf), microgranite, and subordinately, monzogabbro, Ca-silicate rocks, biotite-clinozoisite schist and biotite orthogneiss (restricted to the pre-Pliocene strata). The ubiquitous occurrence of biotite±hornblende monzogranite pebbles in both the Quaternary-Pliocene and Miocene-Oligocene sections, apparently reflects the dominance of these lithologies in the onshore basement, and particularly in the Cambro-Ordovician Granite Harbour Igneous Complex which forms the most extensive outcrop in southern Victoria Land. The petrographical features of the other CRP-2/2A pebble lithologies are consistent with a supply dominantly from areas of the Transantarctic Mountains facing the CRP-2/2A site, and they thus provide further evidence of a local provenance for the supply of basement clasts to the CRP-2/2A sedimentary strata.

Nonlocal electron heat relaxation in a plasma shock at arbitrary ionization number

A recently obtained nonlocal expression for the electron heat flux valid for arbitrary ionization numbers Z is used to study the structure of a plane shock wave in a fully ionized plasma. Nonlocal effects are only important in the foot of the electronic preheating region, where the electron temperature gradient is the steepest. The results are quantified as a function of a characteristic Knudsen number of that region. This work also generalizes to arbitrary values of Z previous results on plasma shock wave structure.

An evaluation of thermal plasmas in pyrometallurgy

The development of reliable, high powered plasma generators has resulted in many plasma processes being proposed as alternatives to existing pyrometallurgical technologies. This work evaluates the advantages and disadvantages of plasma systems by reviewing plasma generators, their integration with reactors and the process economics. Many plasma systems were shown to be technically and economically superior to existing technologies, but some of the plasma system advantages quoted in the literature were found to be impractical because of other system constraints. Process applications were limited by the power inputs available from plasma generators compared to AC electric furnaces. A series of trials were conducted where chromite and steelplant baghouse dusts were smelted in the Tetronics' 2.0 MW transferred arc/open bath reactor to confirm the operating characteristics of the plasma system and its economics. Chromite smelting was technical superior to submerged arc furnace technology, but the economics were unfavourable because of the limited power available from the water-cooled plasma torch and the high electrical energy consumption. A DC graphite electrode plasma furnace using preheated and prereduced chromite concentrates will compete economically with the submerged arc furnace. Ni, Cr and Mo were economically recovered from high alloy content steelplant dusts for recycling. Five Electric Arc Furnace dusts were smelted to produce a non-toxic residue and recover the contained zinc to an enriched zinc oxide product for recycling. It should be possible to condense the zinc vapour directly in a zinc splash condenser to increase the value of the product. Because of the limited power available from plasma generators, plasma processes will be most suitable for treating high and medium value materials such as Au, Pt, Mo, Ni, Ti, V, Cr etc at small production rates, heating metals in tundishes and ladles and remelting superalloy scrap. The treatment of environmentally hazardous waste materials is a particularly interesting application because of the additional financial incentives. Non-transferred arc plasma generators will be used for air and gas preheating in blast furnaces to reduce metallurgical coke consumptions.