18,789 research outputs found

    Finite element simulation of powder compaction via shock consolidation using gas-gun system

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    Shock consolidation is a promising method for consolidation of nanocrystalline metallic powders since it can prevent grain growth of nanopowders during the process due to very short processing time. However, internal cracks often occurs in powder compacts during the shock consolidation process. In this paper, finite element simulations showed that reflected tensile wave causes spall phenomena resulting internal crack of powder compaction during shock compaction process. To reduce spall phenomena, FEM simulation with changing compaction die's geometry was performed to find out relationship between shape and tensile wave intensity. Based on FEM results, new compaction die was designed and bulk nanocrystalline Cu are obtained using new compaction die. (C) 2014 Published by Elsevier Ltd.open1111Ysciescopu

    Printing three-dimensional tissue analogues with decellularized extracellular matrix bioink

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    The ability to print and pattern all the components that make up a tissue (cells and matrix materials) in three dimensions to generate structures similar to tissues is an exciting prospect of bioprinting. However, the majority of the matrix materials used so far for bioprinting cannot represent the complexity of natural extracellular matrix (ECM) and thus are unable to reconstitute the intrinsic cellular morphologies and functions. Here, we develop a method for the bioprinting of cell-laden constructs with novel decellularized extracellular matrix (dECM) bioink capable of providing an optimized microenvironment conducive to the growth of three-dimensional structured tissue. We show the versatility and flexibility of the developed bioprinting process using tissue-specific dECM bioinks, including adipose, cartilage and heart tissues, capable of providing crucial cues for cells engraftment, survival and long-term function. We achieve high cell viability and functionality of the printed dECM structures using our bioprinting method.open11349353sciescopu

    A monolithic and flexible fluoropolymer film microreactor for organic synthesis applications

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    A photocurable and viscous fluoropolymer with chemical stability is a highly desirable material for fabrication of microchemical devices. Lack of a reliable fabrication method, however, limits actual applications for organic reactions. Herein, we report fabrication of a monolithic and flexible fluoropolymer film microreactor and its use as a new microfluidic platform. The fabrication involves facile soft lithography techniques that enable partial curing of thin laminates, which can be readily bonded by conformal contact without any external forces. We demonstrate fabrication of various functional channels (similar to 300 mu m thick) such as those embedded with either a herringbone micromixer pattern or a droplet generator. Organic reactions under strongly acidic and basic conditions can be carried out in this film microreactor even at elevated temperature with excellent reproducibility. In particular, the transparent film microreactor with good deformability could be wrapped around a light-emitting lamp for close contact with the light source for efficient photochemical reactions with visible light, which demonstrates easy integration with optical components for functional miniaturized systems.open1112Ysciescopu

    A cross-cultural study on perceived lighting quality and occupants' well-being between UK and South Korea

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    The path leading from lighting quality through preference and mood to human health and well-being was defined as the ‘Appraisal Path’ by Veitch et al. This study aims to investigate the appraisal path under uncontrolled cafes, and to compare the results between daylit and non-daylit cases as well as the cultural differences between the UK and South Korea. A daylit café and a non-daylit café were chosen for the field survey both in London and Seoul. Then, customers’ experiences and feelings in the cafes were investigated by using a customized questionnaire, in terms of quality of lighting, feelings, attractiveness,satisfaction and eye discomfort. 66 customers (49 for daylit, 17 for non-daylit) were randomly selected and questioned in London and 102 customers (62 for daylit, 40 for non-daylit) participated in the field survey in Seoul. As a result, four different appraisal paths were found. No significant relationship was found between perceived lighting quality and perceived eye discomfort at daylit cafes in both London and Seoul. On the other hand, it was found that perceived lighting quality was a key determinant factor on perceived eye discomfort regardless of the cultural differences at non-daylit cafes. However, there was a significant cultural difference in factors affecting perceived lighting quality

    Creating positive atmosphere and emotion in an office-like environment: A methodology for the lit environment

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    This study investigated whether positive human emotion can be set as a goal through the lighting design process. The study first used a model of emotion – the circumplex model of affect – to characterise four different emotion states (liveliness, relaxation, tense and gloom). Second, five professional lighting designers were recruited and were asked to devise the concepts of each lively and relaxing workspace lit environment. A total of fifteen lighting scenarios with the intention to explore the four emotion states were configured and their emotional effect was investigated through a controlled experiment via a self-reported questionnaire with 42 participants (within-subject design). The results indicate that positive emotions of liveliness can be cued under two lighting settings and that of relaxation under three lighting settings of varying colour temperatures and light distribution. There was also a promising link between perceived atmosphere and human emotion, indicating that atmosphere could be a predictor for human emotion

    Hemodynamic Measurement Using Four-Dimensional Phase-Contrast MRI: Quantification of Hemodynamic Parameters and Clinical Applications

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    Recent improvements have been made to the use of time-resolved, three-dimensional phase-contrast (PC) magnetic resonance imaging (MRI), which is also named four-dimensional (4D) PC-MRI or 4D flow MRI, in the investigation of spatial and temporal variations in hemodynamic features in cardiovascular blood flow. The present article reviews the principle and analytical procedures of 4D PC-MRI. Various fluid dynamic biomarkers for possible clinical usage are also described, including wall shear stress, turbulent kinetic energy, and relative pressure. Lastly, this article provides an overview of the clinical applications of 4D PC-MRI in various cardiovascular regions.113Ysciescopuskc

    High Fidelity Tape Transfer Printing Based On Chemically Induced Adhesive Strength Modulation

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    Transfer printing, a two-step process (i.e. picking up and printing) for heterogeneous integration, has been widely exploited for the fabrication of functional electronics system. To ensure a reliable process, strong adhesion for picking up and weak or no adhesion for printing are required. However, it is challenging to meet the requirements of switchable stamp adhesion. Here we introduce a simple, high fidelity process, namely tape transfer printing(TTP), enabled by chemically induced dramatic modulation in tape adhesive strength. We describe the working mechanism of the adhesion modulation that governs this process and demonstrate the method by high fidelity tape transfer printing several types of materials and devices, including Si pellets arrays, photodetector arrays, and electromyography (EMG) sensors, from their preparation substrates to various alien substrates. High fidelity tape transfer printing of components onto curvilinear surfaces is also illustrated

    Dyon condensation in topological Mott insulators

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    We consider quantum phase transitions out of topological Mott insulators in which the ground state of the fractionalized excitations (fermionic spinons) is topologically non-trivial. The spinons in topological Mott insulators are coupled to an emergent compact U(1) gauge field with a so-called "axion" term. We study the confinement transitions from the topological Mott insulator to broken symmetry phases, which may occur via the condensation of dyons. Dyons carry both "electric" and "magnetic" charges, and arise naturally in this system because the monopoles of the emergent U(1) gauge theory acquires gauge charge due to the axion term. It is shown that the dyon condensate, in general, induces simultaneous current and bond orders. To demonstrate this, we study the confined phase of the topological Mott insulator on the cubic lattice. When the magnetic transition is driven by dyon condensation, we identify the bond order as valence bond solid order and the current order as scalar spin chirality order. Hence, the confined phase of the topological Mott insulator is an exotic phase where the scalar spin chirality and the valence bond order coexist and appear via a single transition. We discuss implications of our results for generic models of topological Mott insulators.Comment: 14 pages, accepted to the New Journal of Physic