Effect of geometry and green density on the anisotropic sintering shrinkage of axisymmetric iron parts

Sintering shrinkage of prior cold compacted iron rings with different geometry (height to wall thickness ratio) and green density in the 6.5–7.3?g/cm³ range was investigated. It displays a minimum at an intermediate green density. Axial, tangential and radial shrinkages are different, due to the gradients of green density along the axial and the radial directions. Therefore, the effect of height on shrinkage and its anisotropy is the result of their effect on the stress distribution in the green parts during cold compaction, and the resulting green density and deformation experienced by the powder. Anisotropy decreases on increasing shrinkage.     

Conjugated polymers with polar side chains in bulk heterojunction solar cell devices

Two polymers with polar side chains, namely poly[2,7‐(9,9‐dioctylfluorene)‐alt‐5,5‐(5',8'‐di‐2‐thienyl‐(2',3'‐bis(3''‐(2‐(2‐methoxyethoxy)ethoxy)phenyl)quinoxaline))] ( P1 ) and poly[2,7‐(9,9‐bis(2‐(2‐methoxyethoxy)ethyl)fluorene)‐alt‐5,5‐(5',8'‐di‐2‐thienyl‐(2',3'‐bis(3''‐(2‐(2‐methoxyethoxy)‐ethoxy)phenyl)quinoxaline))] ( P2 ), were synthesized for solar cell application. A series of bulk heterojunction solar cells were systematically fabricated and characterized by varying the electron‐acceptor materials, processing solvents and thickness of the active layer. The results show that P1 , with a higher molecular weight and good film‐forming properties, performed better. The best device showed an open circuit voltage of 0.87 V, a short circuit current of 6.81 mA cm^?2 and a power conversion efficiency of 2.74% with 1:4 polymer:[6,6]‐phenyl‐C71‐butyric acid methyl ester (PCBM[70]) mixture using o‐dichlorobenzene (o‐DCB) as processing solvent. P2 on the other hand showed a poorer performance with chlorobenzene as processing solvent, but a much improved performance was obtained using o‐DCB instead. Thus, an open circuit voltage of 0.80 V, short circuit current of 6.21 mA cm^?2 and an overall power conversion efficiency of 2.22% were recorded for a polymer:PCBM[70] mixing ratio of 1:4. This is presumably due to the improvement of the morphology of the active layer using o‐DCB as processing solvent. © 2013 Society of Chemical Industry     

Radiation induced dissolution of UO2 based nuclear fuel – A critical review of predictive modelling approaches

Radiation induced dissolution of uranium dioxide (UO₂) nuclear fuel and the consequent release of radionuclides to intruding groundwater are key-processes in the safety analysis of future deep geological repositories for spent nuclear fuel. For several decades, these processes have been studied experimentally using both spent fuel and various types of simulated spent fuels. The latter have been employed since it is difficult to draw mechanistic conclusions from real spent nuclear fuel experiments. Several predictive modelling approaches have been developed over the last two decades. These models are largely based on experimental observations. In this work we have performed a critical review of the modelling approaches developed based on the large body of chemical and electrochemical experimental data. The main conclusions are: (1) the use of measured interfacial rate constants give results in generally good agreement with experimental results compared to simulations where homogeneous rate constants are used; (2) the use of spatial dose rate distributions is particularly important when simulating the behaviour over short time periods; and (3) the steady-state approach (the rate of oxidant consumption is equal to the rate of oxidant production) provides a simple but fairly accurate alternative, but errors in the reaction mechanism and in the kinetic parameters used may not be revealed by simple benchmarking. It is essential to use experimentally determined rate constants and verified reaction mechanisms, irrespective of whether the approach is chemical or electrochemical.     

Symmetric Assumptions in the Theory of Disruptive Innovation: Theoretical and Managerial Implications

The literature on disruptive innovation has convincingly explained why many established firms encounter problems under conditions of discontinuous change. Incumbents fail to invest in new technologies that are not demanded by their existing customers. This argument is grounded in resource dependency theory and the associated assumption that existing customers control a firm's internal resource allocation processes. While the problem of disruptive innovation has been convincingly explained, there is still a need for managerial solutions. We argue that a key reason why such solutions are lacking can be found in the asymmetric assumptions made in the original theory of disruptive innovation. Specifically, we identify two related forms of asymmetry. First, the focal (incumbent) firm is treated as a collection of heterogeneous actors with different preferences, incentives and competencies, whereas firms in the surrounding environment are treated as if they contained no such heterogeneity. Second, the theory of disruptive innovation describes incumbents as controlled by their environment, but has failed to recognize that the environment can also be influenced. In this paper we argue that a more symmetric theory of disruptive innovation – i.e. one that treats all similar entities in the same way – opens up for a range of interesting managerial solutions.     

Getting to grips with automated prepreg handling

Automated manufacturing of composite parts based on prepreg material is receiving increased interest with the rising use of composite materials for high-performance applications. The two main automation alternatives for prepreg layup, automated tape layup and fiber placement, are not cost-effective for all types of products, and manual labor is common for the manufacturing of complex parts in low manufacturing volumes. Alternatives to the two dominant automation solutions have been pursued, but so far these have had a limited impact in industrial applications. This paper presents four different solutions for automated layup of prepreg plies to flat laminates that can be formed in a subsequent forming process, which decrease the system complexity. The solutions target products where the layup of flat laminates today is done manually due to technical limitations or cost considerations. The layup solutions must manage challenges caused by material properties such as low material rigidity and tack, and be able to handle a high number of ply shapes. All four solutions are designed for prepreg that is covered with a stiff backing paper. The aim of the paper is to analyze and compare the four solutions. It can be concluded that the most versatile solution is a dual-arm robot equipped with simple end effectors. The dual-arm solution presents a possibility to control the pick-up and lay-down motions that make peeling motions possible, which is advantageous when picking material that has tacked to the pickup surface.     

The information gap between design engineering and materials supply systems design

This paper focuses on the design of materials supply systems in product development projects. In order to design the materials supply system in parallel with the product, product data must be available to the materials supply systems designers. The aim of this paper is to analyse the information quality of the required product data and to indicate how this information quality can be increased. Empirical data have been gathered through case studies conducted within the manufacturing industry. The empirical data show that it is possible to identify the product data required for materials supply systems design. It is also shown that there is an information gap between design engineering and materials supply systems design. The information quality of the required product data for the materials supply systems design has many imperfections, mainly in terms of accessibility, ease of operation, timeliness, understandability, interpretability, relevancy, and completeness. The information quality can be improved by the use of PDM systems, which are especially useful for facilitating an increase in accessibility, ease of operation, and timeliness.     

Parallel enzymatic and non-enzymatic formation of zinc protoporphyrin IX in pork

Zinc protoporphyrin is formed in pork homogenates in both enzymatic and non-enzymatic reactions. Ferrochelatase is active in formation of the highly fluorescent pigment known from Parma ham as demonstrated by inhibition with N-methylmesoporphyrin and by thermal inactivation. A non-enzymatic transmetallisation reaction, exchange of iron in myoglobin by zinc(II), is demonstrated by Pb(II) inhibition of zinc protoporphyrin formation at low Pb(II) concentrations, but promoted at higher Pb(II) concentrations. The non-enzymatic reaction is characterised as a slow bimolecular reaction between protoporphyrin IX and zinc(II) with a second-order rate constant of 0.63 l mol⁻¹ s⁻¹ at 35 °C and a high energy of activation of 98 kJ mol⁻¹ for acetone:water (3:1, v/v) as solvent. Zinc protoporphyrin formation is concluded to be thermodynamically controlled with a formation constant of 4 × 10⁵ M (35 °C, acetone:water (3:1)). An efficient inhibition of formation of zinc protoporphyrin by nitrite is related to myoglobin as substrate and involves both enzymatic and non-enzymatic reactions.