Testing of PTA automatic braze-welding technology for producing absorber joints of solar collectors

The article presents research aimed at developing a PTA braze-welding technology for producing absorber connections between tubes and copper foil with EcoBraz 38102 self-fusible brazing solder in the form of wire 1 mm in diameter. Braze-welding process was carried out by means of two techniques of braze welding of flat copper foil to a tube, while the foil had a 0–1.5 mm wide gap: a connection with a butt joint made by braze welding with simultaneous stamping of a semi-circular channel in the copper foil (the channel diameter equal to the tube diameter); and a connection with two braze-welded fillet joints. Metallographic tests, hardness measurement, static tensile test and thermal conduction efficiency test were performed to determine the properties of prepared connections. It was demonstrated that there exists a field of PTA braze-welding parameters which assures high quality of absorber connections between tubes and copper foil.     

Transient modeling of zinc extraction with D2EHPA in a Kühni column

The transient extraction of zinc sulfate with D2EHPA (di-2-ethylhexyl phosphoric acid) in a section of a Kühni column operated with total recirculation of liquid phases was modeled using the back-mixing and the forward-mixing approaches. The mathematical developments for both models as well as their numerical solutions are given in detail. Operating parameters were calculated using recommended correlations available in the literature and simulations were confronted with experimental data. Both models revealed to describe column operation adequately under evaluated conditions. In addition, as back-mixing and forward-mixing approaches are particularly equivalent in very stirred conditions, the former approach seems to be more advantageous to describe practical situations due to its simplicity in comparison to the later approach.     

Effect of Grain Thermal Expansion Mismatch on Thermal Conductivity of Porous Ceramics

Many ceramics contain microcracks, which are often situated between sintered grains. These microcracks constitute thermal resistances, which may affect heat transfer through the material and its effective thermophysical properties. The thicknesses and the contact areas of the microcracks change with temperature as a result of the thermal expansion mismatch between the grains on opposite sides of the microcracks. This physical mechanism affects changes of the material's thermal conductivity, k , with temperature. The above mechanism usually plays a minor role at atmospheric pressure, where heat may flow via the gas filling the cracks. Hence, the temperature-induced changes of the crack geometry have little effect on heat transfer. However, at low gas pressures, where the heat flow between the grains occurs mainly via the contact areas, the grains' thermal expansion mismatch causes unusual temperature behavior of the material's thermal conductivity observed for several industrial refractories. In this paper, the influence of the above physical mechanism is discussed relative to other heat transfer mechanisms described in the literature. A simple physical model of the thermal expansion of grains bonded by an agent, having different thermal expansion coefficients, is developed. This model allows calculation of the contact area and the average microcrack opening between the grains as functions of the temperature, the characteristic grains sizes and their thermal expansion coefficients, and the permanent crack area. These parameters are evaluated and used to calculate the effective thermal conductivity of ceramic materials containing microcracks that appear as a result of thermal contraction of grains. The calculated thermal conductivity satisfactorily correlates with the experimental data collected for several chrome-magnesite refractories over a wide range of temperatures and gas pressures.     

Investigation on formability enhancement of 5A06 aluminium sheet by impact hydroforming

High strain rate (HSR) forming has been found to be able to enhance the formability of sheet metals like electro-magnetic forming. Impact hydroforming (IHF) is proposed, in which the sheet is formed with high-pressure pulse combining hydroforming and HSR forming. An IHF bulge test setup was designed, 5A06 aluminium sheet was tested with strain rate of 2 × 10³ s^?1 showing remarkable thickness strain increase compared with quasi-static condition. A new IHF equipment is designed, the IHF process was verified effective with the equipment, complicated aluminium aircraft sheet part with high drawing ratio was formed that cannot be formed with quasi-static hydroforming.     

Application of Ozone in Full-Scale to Reduce Filamentous Bulking Sludge at Öresundsverket WWTP

The return sludge of one of the four treatment lines at Öresundsverket WWTP in Sweden was subjected to ozonation in full-scale to reduce filamentous bulking sludge. The biological nitrogen and phosphorus removal capacity along with effluent parameters were studied throughout the trial. Samples were also taken to track possible changes in microbial population due to ozone. 2.8–5.0 g O₃ kg^?1 treated SS^?1 reduced the DSVI of the ozone-treated line from 170 to 100 mL g^?1 and the reference line remained at 150 mL g^?1. No adverse effect on the biological nitrification- or the phosphorus removal rates could be detected. The microbial population of the two lines did not exhibit any substantial changes which can be correlated to ozone addition.     

Forced assembly by multilayer coextrusion to create oriented graphene reinforced polymer nanocomposites

A potential advantage of platelet-like nanofillers as nanocomposite reinforcements is the possibility of achieving two-dimensional stiffening through planar orientation of the platelets. The ability to achieve improved properties through in-plane orientation of the platelets is a challenge and, here, we present the first results of using forced assembly to orient graphene nanoplatelets in poly(methyl methacrylate)/polystyrene (PMMA/PS) and PMMA/PMMA multilayer films produced through multilayer coextrusion. The films exhibited a multilayer structure made of alternating layers of polymer and polymer containing graphene as evidenced by electron microscopy. Significant single layer reinforcement of 118% at a concentration of 2 wt % graphene was achieved—higher than previously reported reinforcement for randomly dispersed graphene. The large reinforcement is attributed to the planar orientation of the graphene in the individual polymer layers. Anisotropy of the stiffening was also observed and attributed to imperfect planar orientation of the graphene lateral to the extrusion flow.     

A 122 TΩ Hz transimpedance bandwidth product BiCMOS optical sensor front-end with a 54.7 dB voltage-controlled photo-sensitivity range

An optical sensor front-end with integrated PIN photodiode in 0.6 μm BiCMOS technology intended for universal optical storage operation is presented. It is based on a mixed current conveyor and voltage amplifiers topology avoiding stability problems. The transimpedance is continuously variable and directly proportional to a voltage-controlled resistance. Another voltage-controlled resistor within a variable-gain voltage amplifier increases the photo-sensitivity range. A fixed-gain voltage amplifier and a current biasing of the current conveyor enable frequency bandwidth enhancement leading to a large transimpedance bandwidth product. A linearity error smaller than 2.8%, a photo-sensitivity range of 541 (54.7 dB) with the largest photo-sensitivity of 2468 mV/μW, an offset voltage <13.7 mV, a frequency bandwidth up to 277 MHz, a slew rate up to 377 V/μs, a transimpedance bandwidth product up to 122 TΩ Hz, and a maximum power consumption of <4.3 mW are achieved.     

Assessment of GH1, CAPN1 and CAST polymorphisms as markers of carcass and meat traits in Bos indicus and Bos taurus–Bos indicus cross beef cattle

The objective of this study was to investigate the effects of bovine GH1, CAPN1 and CAST gene polymorphisms on carcass and meat traits in Nellore and Nellore x Bos taurus beef cattle. Three hundred animals were genotyped for GH1/MspI (TC/G in intron 3), CAPN316 (AF_252504.2:g.5709C > G) and CAST/RsaI (AY_008267.1:g282C > G) and phenotyped for rib eye area, backfat thickness, intramuscular fat, shear force (SF), and myofibrillar fragmentation index (MFI). No significant associations were observed between the GH1/MspI and CAST/RsaI polymorphisms and phenotypes, although the relation between the CAST/RsaI genotypes and meat tenderness evaluated by MFI approached significant. The fact that the CAPN316 polymorphism did not show adequate segregation in Nellore cattle confirms the difficulty of using this marker in breeding programs of different Bos indicus breeds. However, the positive results of the association analysis obtained for Nellore x B. taurus crosses contributed to the validation of previous findings.