Design optimization of hot stamping tooling produced by additive manufacturing

The design flexibility of Additive Manufacturing (AM) can be utilized to develop innovative and sustainable hot stamping tools with enhanced quenching capability compared to tools manufactured by conventional manufacturing processes. This study proposes a concept for hot stamping tools with integrated lattice structures that selectively substitute a die's solid areas. A lattice structure demonstrates reduced thermal mass and can affect the ability of the tool to absorb heat from the blank and the rate at which the tool is cooled between two consecutive stamping cycles. This study explores the design space of a hot stamping tool with integrated lattice structures. It presents the optimized design for an effective compromise between cooling performance, structural integrity, and several other design parameters shown in the study. The proposed method utilizes a 2D thermo-mechanical finite element analysis model of a single cooling channel combined with Design of Experiments (DoE) to reduce the computational cost. The results show that the integration of lattice structure cannot only deliver improved cooling performance with minimum change in the dimensions of the cooling system but also achieves a faster AM build time since less material is required to be printed

Understanding the impact of convective ethanol humidity on the precipitation behaviour of dissolved lactose in a water droplet

Crystalline lactose particles, composed of agglomerated ultrafine crystallites, were produced using the antisolvent vapour precipitation technique. This technique exposes a single suspended aqueous lactose droplet to a convective stream laden with ethanol vapour. Manipulating simultaneous ethanol absorption and water evaporation from the droplet by adjusting the ethanol vapour humidity, led to various crystallite morphologies. Within the intermediate and high ranges of the ethanol humidity tested, higher humidity led to finer and more dendritic-like crystallites. Surprisingly, low ethanol humidity (20% ERH) led to a relatively high rate of ethanol concentration increment in the droplet but inadvertently exhibited a low nucleation potential. Thus, the crystallization potential of a lactose droplet under antisolvent vapour precipitation conditions will need to be evaluated in terms of the rate of ethanol concentration increment as well as the solute concentration-ethanol concentration history. These factors will be important in controlling or scaling up the antisolvent vapour precipitation technique

Understanding the formation of ultrafine maltodextrin particles under simultaneous convective drying and antisolvent vapour precipitation

Research on simultaneous antisolvent-vapour-induced precipitation and convective drying of a solute-containing droplet was extensively conducted since this technique was introduced. However, the internal droplet compositions, which were suggested to be related to the formation of particle morphologies, had not been explored. Herein, the ethanol-vapour-induced precipitation of multi-solvent droplets containing maltodextrin as the solute was used to analyse internal droplet compositions. The droplet mass and diameter profiles were obtained via an established single-droplet drying experiment, which mimicked the spray drying of droplets. Analysis revealed that the antisolvent concentration increased with time and was higher than solvent concentration towards the end of the process. It is interesting to find out that the final particle morphology was profoundly impacted by the ambient ethanol humidity and also how spontaneous the subsequent drying was during ethanol-vapour-induced precipitation of the solutes. The formation of the porous structure was favoured with the occurrence of spontaneous vaporization once the ethanol was present for precipitation. Therefore, low ethanol humidity (20% ERH in this study) was sufficient. In contrast, higher ethanol humidity (>70% ERH) was preferable to produce spherical particles. This study provides an insight into particle engineering to unveil the internal droplet conditions and physical phenomena during this unique process

Characteristic free volume change of bulk metallic glasses

2011-2012 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe

Characteristic free volumes of bulk metallic glasses : measurement and their correlation with glass-forming ability

2010-2011 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe

The signalling channel of Central Bank interventions:modelling the Yen/US dollar exchange rate

This paper presents a theoretical framework analysing the signalling channel of exchange rate interventions as an informational trigger. We develop an implicit target zone framework with learning in order to model the signalling channel. The theoretical premise of the model is that interventions convey signals that communicate information about the exchange rate objectives of the central bank. The model is used to analyse the impact of Japanese FX interventions during the period 1999--2011 on the yen/US dollar dynamics

Mott physics and band topology in materials with strong spin-orbit interaction

Recent theory and experiment have revealed that strong spin-orbit coupling can have dramatic qualitative effects on the band structure of weakly interacting solids. Indeed, it leads to a distinct phase of matter, the topological band insulator. In this paper, we consider the combined effects of spin-orbit coupling and strong electron correlation, and show that the former has both quantitative and qualitative effects upon the correlation-driven Mott transition. As a specific example we take Ir-based pyrochlores, where the subsystem of Ir 5d electrons is known to undergo a Mott transition. At weak electron-electron interaction, we predict that Ir electrons are in a metallic phase at weak spin-orbit interaction, and in a topological band insulator phase at strong spin-orbit interaction. Very generally, we show that with increasing strength of the electron-electron interaction, the effective spin-orbit coupling is enhanced, increasing the domain of the topological band insulator. Furthermore, in our model, we argue that with increasing interactions, the topological band insulator is transformed into a "topological Mott insulator" phase, which is characterized by gapless surface spin-only excitations. The full phase diagram also includes a narrow region of gapless Mott insulator with a spinon Fermi surface, and a magnetically ordered state at still larger electron-electron interaction.Comment: 10+ pages including 3+ pages of Supplementary Informatio

Learning and innovative elements of strategy adoption rules expand cooperative network topologies

Cooperation plays a key role in the evolution of complex systems. However, the level of cooperation extensively varies with the topology of agent networks in the widely used models of repeated games. Here we show that cooperation remains rather stable by applying the reinforcement learning strategy adoption rule, Q-learning on a variety of random, regular, small-word, scale-free and modular network models in repeated, multi-agent Prisoners Dilemma and Hawk-Dove games. Furthermore, we found that using the above model systems other long-term learning strategy adoption rules also promote cooperation, while introducing a low level of noise (as a model of innovation) to the strategy adoption rules makes the level of cooperation less dependent on the actual network topology. Our results demonstrate that long-term learning and random elements in the strategy adoption rules, when acting together, extend the range of network topologies enabling the development of cooperation at a wider range of costs and temptations. These results suggest that a balanced duo of learning and innovation may help to preserve cooperation during the re-organization of real-world networks, and may play a prominent role in the evolution of self-organizing, complex systems.Comment: 14 pages, 3 Figures + a Supplementary Material with 25 pages, 3 Tables, 12 Figures and 116 reference