A new one-phase material model for the numerical prediction of critical material flow conditions in thixoforging processes

Thixoforging allows one-step forming processes of near-net shape components having excellent mechanical properties. However, the high sensitivity of thixoforging regarding process conditions requires precise modelling and determination of process related parameters. At the same time, simple numerical design proves challenging because of the inaccuracy of existing one-phase material models regarding the shear thinning flow behaviour of semi solid metals. Consequently, this paper deals with the development of a new one-phase material model providing a more precise simulation of materials’ shear rate dependency. By using this model, simulations could be performed, which allowed the prediction of solidification and flow-related component defects.     

The impact of different hop compounds on the growth of selected beer spoilage bacteria in beer

Beer spoiling lactic acid bacteria are a major reason for quality complaints in breweries around the world. Spoilage by a variety of these bacteria can result in haze, sediment, slime, off-flavours and acidity. As these bacteria occur frequently in the brewing environment, using certain hop products that inhibit the growth of these spoilers could be a solution to prevent problems. To investigate the impact of seven different hop compounds (α-acids, iso-α-acids, tetrahydro-iso-α-acids, rho-iso-α-acids, xanthohumol, iso-xanthohumol and humulinones) on the growth of six major beer spoilage bacteria (Lactobacillus brevis. L. backi, L. coryniformis, L. lindneri, L. buchneri, Pediococcus damnosous), two concentrations (10 and 25 mg/L) of each hop substance were added to unhopped beer. The potential growth of the spoilage bacteria was investigated over 56 consecutive days. A comparison of the results shows a strong inhibition of growth of all spoilage bacteria at 25 mg/L of tetrahydro-iso-α-acids closely followed by α-acids as the second most inhibitory substance. The results showed a high resistance of L. brevis to all hop compounds as well as an inhibition of L. coryniformis and L. buchneri at low concentrations of most hop components. In comparison with the control sample, L. lindneri showed increased growth in the presence of some hop compounds (rho-iso-α-acids, xanthohumol, iso-xanthohumol, humulinones). © 2020 The Authors. Journal of the Institute of Brewing published by John Wiley & Sons Ltd on behalf of The Institute of Brewing & Distilling     

Characterization and determination of brewer's solid wastes composition

Agro‐industrial wastes are produced in large quantities around the world from the processing and manufacturing of food and beverages. The disposal of these wastes into the environment leads to damage to ecosystems owing to their composition rich in organic matter. In this context it may be noted that the brewing industry, whose production process includes processing steps and fermentation of vegetable raw materials such as barley and/or other grains used as adjuncts and hops, generates various byproducts. The worldwide consumption of these beverages and the current model of breweries, which includes production on a large scale, lead to the generation of large amounts of brewery waste, namely spent grain, hot trub and residual yeast. Owing to its composition, these residues exhibit significant potential for application in bioprocess technologies. In this study the three residues mentioned had their composition determined as a function of moisture, ash, total organic carbon (TOC), total and soluble nitrogen, reducing sugar and soluble free amino nitrogen. Moreover, the residues were characterized for total acidity, pH and chemical oxygen demand (COD) of total and soluble fractions. The three residues evaluated had high moisture content (>80%) and high organic matter content (TOC and COD, ~50% and >1000 mg/g, respectively), which can highlights the significant protein fraction (almost 50% for hot trub and residual yeast), suggesting the possibility of using these wastes for recovery. Copyright © 2015 The Institute of Brewing & Distilling     

Cytotoxicity of fipronil on mice liver cells

In the present study, mice livers were examined following exposure to different doses of fipronil (15, 25, and 50 mg/kg). Histological and histochemical techniques were used to determine the cytotoxic potential of this compound and to assess the damage it caused to livers. Mice were divided into four groups: control group and groups I, II, and III were exposed to 15, 25, and 50 mg/kg fipronil, respectively. Our findings revealed cytological, morphohistological, and histochemical alterations in liver cells of animals from groups I, II, and III compared to group control animals. These changes included Kupffer-cell proliferation, hepatocyte hypertrophy, accumulation and distribution of proteins, polysaccharides, lipids, and vacuoles in the cytoplasm of hepatocytes, and congestion of blood vessels. These phenotypes mainly characterize the following: (a) autophagic processes, (b) steatosis, and (c) cell death by necrosis, which demonstrate the damage caused by fipronil on nontarget organisms in artificial conditions.     

Hierarchical Rasterization of Curved Primitives for Vector Graphics Rendering on the GPU

In this paper, we introduce the CPatch, a curved primitive that can be used to construct arbitrary vector graphics. A CPatch is a generalization of a 2D polygon: Any number of curves up to a cubic degree bound a primitive. We show that a CPatch can be rasterized efficiently in a hierarchical manner on the GPU, locally discarding irrelevant portions of the curves. Our rasterizer is fast and scalable, works on all patches in parallel, and does not require any approximations. We show a parallel implementation of our rasterizer, which naturally supports all kinds of color spaces, blending and super‐sampling. Additionally, we show how vector graphics input can efficiently be converted to a CPatch representation, solving challenges like patch self intersections and false inside‐outside classification. Results indicate that our approach is faster than the state‐of‐the‐art, more flexible and could potentially be implemented in hardware.     

Conjugate heat transfer through nano scale porous media to optimize vacuum insulation panels with lattice Boltzmann methods

Due to reduced thermal conductivity, vacuum insulation panels (VIPs) provide significant thermal insulation performance. Our novel vacuum panels operate at reduced pressure and are filled with a powder of precipitated silicic acid to further hinder convection and provide static stability against atmospheric pressure. To obtain an in depth understanding of heat transfer mechanisms, their interactions and their dependencies inside VIPs, detailed microscale simulations are conducted.Particle characteristics for silica are used with a discrete element method (DEM) simulation, using open source software Yade-DEM, to generate a periodic compressed packing of precipitated silicic acid particles. This aggregate packing is then imported into OpenLB (openlb.net) as a fully resolved geometry, and used to study the effects on heat transfer at the microscale. A three dimensional Lattice Boltzmann method (LBM) for conjugated heat transfer is implemented with open source software OpenLB, which is extended to include radiative heat transport. The infrared intensity distribution is solved and coupled with the temperature through the emissivity, absorption and scattering of the studied media using the radiative transfer equation by means of LBM. This new holistic approach provides a distinct advantage over similar porous media approaches by providing direct control and tuning of particle packing characteristics such as aggregate size, shape and pore size distributions and studying their influence directly on conduction and radiation independently. Our aim is to generate one holistic tool which can be used to generate silica geometry and then simulate automatically the thermal conductivity through the generated geometry.     

Structural and Chemical Changes to CH3NH3PbI3 Induced by Electron and Gallium Ion Beams

Organic–inorganic hybrid perovskites, such as CH₃NH₃PbI_3, have shown highly promising photovoltaic performance. Electron microscopy (EM) is a powerful tool for studying the crystallography, morphology, interfaces, lattice defects, composition, and charge carrier collection and recombination properties at the nanoscale. Here, the sensitivity of CH₃NH₃PbI₃ to electron beam irradiation is examined. CH₃NH₃PbI₃ undergoes continuous structural and compositional changes with increasing electron dose, with the total dose, rather than dose rate, being the key operative parameter. Importantly, the first structural change is subtle and easily missed and occurs after an electron dose significantly smaller than that typically applied in conventional EM techniques. The electron dose conditions under which these structural changes occur are identified. With appropriate dose‐minimization techniques, electron diffraction patterns can be obtained from pristine material consistent with the tetragonal CH₃NH₃PbI₃ phases determined by X‐ray diffraction. Radiation damage incurred at liquid nitrogen temperatures and using Ga⁺ irradiation in a focused ion beam instrument are also examined. Finally, some simple guidelines for how to minimize electron‐beam‐induced artifacts when using EM to study hybrid perovskite materials are provided.     

Efficient and accurate simulation of the packaging forming process

To allow for large‐scale forming applications, such as converting paperboard into package containers, efficient and reliable numerical tools are needed. In finite element simulations of thin structures, elements including structural features are required to reduce the computational cost. Solid‐shell elements based on reduced integration with hourglass stabilization is an attractive choice. One advantage of this choice is the natural inclusion of the thickness, not present in standard degenerated shells, which is especially important for many problems involving contact. Furthermore, no restrictions are imposed on the constitutive models since the solid‐shell element does not require the plane stress condition to be enforced. In this work, a recently proposed efficient solid‐shell element is implemented together with a state‐of‐the‐art continuum model for paperboard. This approach is validated by comparing the obtained numerical results with experimental results for paperboard as well as with those found by using 3D continuum elements. To show the potential of this approach, a large‐scale forming simulation of paperboard is used as a proof of concept.