Theoretical perspectives on localized knowledge spillovers and agglomeration

Empirical evidence shows that innovation is geographically concentrated, but whether localized knowledge spillovers provide a logically valid explanation for this phenomenon is unclear. I show that in the context of cost‐reducing R&D spillovers between Cournot oligopolists the explanation is plausible: localized knowledge spillovers encourage agglomeration, but whether this leads to higher levels of effective R&D depends on the extent of the spillovers, the number of firms, and the industry's R&D efficiency. Contrary to the earlier theoretical work, this illustrates a context, in which the localized knowledge spillover explanation is actualized, and provides necessary conditions, which can be empirically tested.     

Microstructure and electrical properties of plasma sprayed Gd0.15Ce0.85O2-δ coatings from solution combustion synthesized flowable powders

Powders of Gadolinia doped Ceria (Gd_0.15Ce_0.85O_2-δ (GDC)), a promising electrolyte material for intermediate temperature solid oxide fuel cell has been prepared by solution combustion (SC) synthesis. Variation of fuel to oxidizer ratio in the synthesis results in the GDC powder with varied powder characteristics. Fuel deficient combustion reaction results in GDC powder with smaller crystallites size but with larger agglomerates; whereas reaction with near stochiometric amount of fuel leads to the GDC powder with larger crystallite size and smaller agglomerates. Powders with large agglomerates possess required particle size, shape and flowability characteristics appropriate for plasma spraying. Electrolyte coatings fabricated from the synthesized plasma spray grade powders exhibit superior inter splat adhesion and conductivity (∼0.02 S/cm at 600 °C). Dense nature of the coating is ascribed to the complete melting of the porous GDC particles in the plasma flame. Powders prepared with stochiometric fuel are suitable for tape casting process.     

DRYING AND DEWATERING R&D IN JAPAN

Presently, it has become an urgent and important concern worldwide to reduce the volume of waste and rationally use the waste for electric power generation. Sludge is a dominant part in the family of wastes. Drying of sludge, not only for volume reduction but also for further utilization, is becoming an essential and integral process. On the other hand, as the requirement of new materials production, for example, fine particles of micron or sub-micron scale for advanced materials, some new drying technologies and techniques have emerged. The market-pull may be the direct and active impetus to drying research and development (R&D). In this paper, drying technologies for sludges, fine particles, coatings as well as advanced dewatering are discussed to reflect the “hot” points of drying and dewatering R&D in Japan. And some novel dryers are also presented.     

Bouillon cube process design by applying product driven process synthesis

Unilever produces Knorr™ bouillon cubes for last several decades in various regions like Africa, Caribbean Islands, Central and Eastern Europe, and Russia etc. This high volume business generates revenues of an order of €1 bn/year. This article describes our approach for conceptual design of bouillon cube manufacturing process. Consumer attributes need to be taken into account while process design for such products. In this paper we used the product driven process synthesis approach for conceptual design of bouillon cube manufacturing process. In this approach we, based on the consumer attributes, defined the fundamental tasks to convert inputs (raw materials) into the desired outputs (bouillon cube microstructure). Given these fundamental tasks, logical alternative process flow sheets were generated. The most promising of these alternatives were experimentally tested. We found that by spraying the binder and selective granulation of less flowing ingredients increased homogeneity and flow-ability of the granules which also resulted into higher cube hardness. This has a positive influence on the consumer attributes. Using this novel process, we also demonstrated potential formulation flexibility and cost savings due to a reduction of fat and flow-agent as well as potential reduction of “maturation time”.     

Accelerated fluid bed drying using NIR monitoring and phenomenological modeling

A “fast-drying” method to accelerate the fluid bed drying process is presented. It relies on concepts of heat and mass transfer with real-time near-infrared (NIR) monitoring of moisture. Triplicate trials show that fast drying can reduce granulation drying time by half over single-temperature cycles. The product is equivalent in every way tested to material made using a conventional cycle even though the inlet temperature throughout the constant-rate stage was higher than the melting point of the compound. Tablets made from the fast-dried granulation exhibit equivalent physical characteristics to tablets made from granulations dried at a single, lower temperature.     

乳胶型附聚剂附聚作用的实验研究

本文研究了以一种胶乳附聚另一种胶乳的基本规律。研究了附聚后乳胶粒粒径及其分布,探讨了各种影响因素。本文发现,随着附聚胶乳用量的增大,存在两个附聚峰。     

Rheology of methane hydrate slurries during their crystallization in a water in dodecane emulsion under flowing

An original experimental set-up was developed and used for studying crystallization and rheology of methane hydrate/water/dodecane system. Methane is injected in a water in dodecane emulsion at low temperature and high pressure in order to form methane hydrate crystals and to move the suspension by gas lift. It behaves as a Newtonian fluid. Dynamic viscosity and conversion of water and gas into gas hydrate crystals were measured during the process for various water contents. Experimental results were explained by means of a model including nucleation, growth and agglomeration. Due to the high value of crystal and drop concentrations, agglomeration takes place through three-body collisions between one water drop and two already formed agglomerates. Resulting agglomerates were considered as fractal-like ones. During crystallization and agglomeration, the effective volume fraction of drops and porous agglomerates is increased, and then suspension viscosity increases. When all water drops are crystallized, agglomeration stops and viscosity does not change.     

Process of extrusion in the unit of special design

Extrusion of paste materials is a means of processing powder materials to a granulated form. A powder material is mixed with a liquid and transformed to the form of paste. The paste has to have the appropriate flow properties to be able to be extruded. This is very important especially in the area of reduction between the barrel and die. There is the place where the paste has to deform itself and to flow into the holes of die that have a smaller cross section than is in the barrel. It is the zone where the rheology properties of paste and its speed have the biggest influence on the extrusion pressure. It can even happen that the paste can be dewatered under the pressure gradient in this place. If the rotor with blades is situated in this zone it has a positive influence on the process of extrusion. This element has an influence on the rate of shear strain and decreasing of the apparent viscosity with a following drop in the extrusion pressure. This paper describes research of the process of extrusion in equipment with separated drives of the screw and a rotor that is placed in the input zone in the hole of matrix. First influence of the operating speeds of screw and rotor on extrusion pressure is studied here, then it is compared with the torque that is needed for the drive of the rotor. According to the results it is evident that the extrusion pressure increases with the accrual of the speed of flowing paste and decreases with the increase of the rotors operating speed. The influence of flowing paste on the torque is complicated. There is an interval where the torque goes up and then an interval in which the torque decreases. The results of experiments confirmed that the rotor has a positive influence on the process of extrusion.We would like to thank the Grant Agency of the Slovak Republic for supporting our research work performed in the frame of Grant Project No.1/8092/01.     

Interspecies electron transfer in methanogenic propionate degrading consortia

Propionate is a key intermediate in the conversion of complex organic matter under methanogenic conditions. Oxidation of this compound requires obligate syntrophic consortia of acetogenic proton- and bicarbonate reducing bacteria and methanogenic archaea. Although H(2) acts as an electron-carrier in these consortia, evidence accumulates that formate plays an even more important role. To make energy yield from propionate oxidation energetically feasible for the bacteria and archaea involved, the concentrations of H(2) and formate have to be extremely low. On the other hand, the diffusion distance of these carriers has to be small to allow high propionate conversion rates. Accordingly, the high conversion rates observed in methanogenic bioreactors are due to the fact that the propionate-oxidizing bacteria and their methanogenic partners form micro-colonies within the densely packed granules.