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Virtual reality-based assembly-level design for additive manufacturing decision framework involving human aspects of design
No full textThere is a combinatorial explosion of alternative variants of an assembly design owing to the design freedom provided by additive manufacturing (AM). In this regard, a novel virtual reality-based decision-support framework is presented herein for extracting the superior assembly design to be fabricated by AM route. It specifically addresses the intersection between human assembly and AM hence combining design for assembly, and design for additive manufacturing using axiomatic design theory. Several virtual reality experiments were carried out to achieve this with human subjects assembling parts. At first, a two-dimensional table is assembled, and the data are used to confirm the independence of non-functional requirements such as assembly time and assembly displacement error according to independence axiom. Then this approach is demonstrated on an industrial lifeboat hook with three assembly design variations. The data from these experiments are utilized to evaluate the possible combinations of the assembly in terms of probability density based on the information axiom. The technique effectively identifies the assembly design most likely to fulfill the non-functional requirements. To the authors??? best knowledge, this is the first study that numerically extracts the human aspect of design at an early design stage in the decision process and considers the selection of the superior assembly design in a detailed design stage. Finally, this process is automated using a graphical user interface, which embraces the practicality of the currently integrated framework and enables manufacturers to choose the best assembly design
Suboptimal Mitochondrial Activity Facilitates Nuclear Heat Shock Responses for Proteostasis and Genome Stability
No full textThermal stress induces dynamic changes in nuclear proteins and relevant physiology as a part of the heat shock response (HSR). However, how the nuclear HSR is fine-tuned for cellular homeostasis remains elusive. Here, we show that mitochondrial activity plays an important role in nuclear proteostasis and genome stability through two distinct HSR pathways. Mitochondrial ribosomal protein (MRP) depletion enhanced the nucleolar granule formation of HSP70 and ubiquitin during HSR while facilitating the recovery of damaged nuclear proteins and impaired nucleocytoplasmic transport. Treatment of the mitochondrial proton gradient uncoupler masked MRP-depletion effects, implicating oxidative phosphorylation in these nuclear HSRs. On the other hand, MRP depletion and a reactive oxygen species (ROS) scavenger non-additively decreased mitochondrial ROS generation during HSR, thereby protecting the nuclear genome from DNA damage. These results suggest that suboptimal mitochondrial activity sustains nuclear homeostasis under cellular stress, providing plausible evidence for optimal endosymbiotic evolution via mitochondria-to -nuclear communication
Facile and adhesive-free method for bonding nanofiber membrane onto thermoplastic polystyrene substrate to fabricate 3D cell culture platforms
No full textNanofiber (NF) membranes have been highlighted as functional materials for biomedical applications owing to their high surface-to-volume ratios, high permeabilities, and extracellular matrix-like biomimetic structures. Because many in vitro platforms for biomedical applications are made of thermoplastic polymers (TP), a simple and leak-free method for bonding NF membranes onto TP platforms is essential. Here, we propose a facile but leak-free localized thermal bonding method for integrating 2D or 3D-structured NF membrane onto a TP supporting substrate while preserving the pristine nanofibrous structure of the membrane, based on localized preheating of the substrate. A methodology for determining the optimal preheating temperature was devised based on a numerical simulation model considering the melting temperature of the NF material and was experimentally validated by evaluating bonding stability and durability under cell culture conditions. The thermally-bonded interface between the NF membrane and TP substrate was maintained stably for 3 weeks allowing the successful construction of an intestinal barrier model. The applicability of the localized thermal bonding method was also demonstrated on various combinations of TP materials (e.g., polystyrene and polymethylmethacrylate) and geometries of the supporting substrate, including a culture insert and microfluidic chip. We expect the proposed localized thermal bonding method to contribute toward broadening and realizing the practical applications of functional NF membranes in various biomedical fields
Application of green hydrogen with theoretical and empirical approaches of alkaline water electrolysis: Life cycle-based techno economic and environmental assessments of renewable urea synthesis
No full textAlkaline water electrolysis which is the most commercialized and mature technology of water electrolysis was researched to improve performance by the Korea Institute of Energy Research (KIER). In line with the trend of energy shift, renewable urea production through hydrogen production from alkaline water electrolysis was proposed in this work. To vali-date the process modeling of renewable urea production and hydrogen performance analysis with I-V curves was assessed. Economic and life cycle assessments were conducted to provide quantitative guidelines for renewable urea production. Absolutely, the influential factor of unit urea production cost was hydrogen from alkaline water electrolysis and environmental assessment results as well. Moreover, the guidelines for renewable urea production were provided through cost estimation and life cycle assess-ment. In summary, hydrogen production from alkaline water electrolysis had a significant impact on urea production and for this reason, research on alkaline water electrolysis should continue for further development.(c) 2023 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved
Dynamic performance of industrial robots in the secondary carbon fiber-reinforced plastics machining
No full textCarbon fiber-reinforced plastics (CFRPs) find many applications given their superior properties. These materials are usually formed using a near-net-shape method that requires secondary machining, such as drilling and trimming, after molding. Industrial robots are becoming increasingly popular machining tools in industries exhibiting high demand for CFRPs. However, it remains challenging to achieve high dimensional accuracy when using such robots and dynamic performance is poor. We experimentally investigated the dynamic properties of the tool tip according to the dominant robot posture during CFRP secondary machining. Based on the results, multi-layer perceptron models were developed to predict the dominant natural frequency and dynamic stiffness of the tool tip. The minimum and maximum mean absolute percentage errors were 1.99 and 7.94, respectively; the error changed markedly with robot posture. Our models improved CFRP robotic machinability. Experimentally, the delamination rates of drilled holes decreased by 15 % and 75 % in terms of length and area, respectively, and the trimmed surface roughness improved by 27 %