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arXiv 2025年

作者： Hur, Matthew Bartol, Thomas Rangamani, Padmini Sejnowski, Terrence Mjolsness, Eric Program in Mathematical Computational and Systems Biology Univeristy of California Irvine IrvineCA United States Computational Neurobiology Laboratory Salk Institute for Biological Studies La Jolla CA United States Departments of Pharmacology and Mechanical and Aerospace Engineering University of California San Diego La Jolla CA United States Deparment of Neurobiology University of California San Diego La Jolla CA United States Departments of Computer Science and Mathematics Univeristy of California Irvine IrvineCA United States

There is a morphodynamic component to synaptic learning by which changes in dendritic (postsynaptic) spine head size are associated with the strengthening or weakening of the synaptic connection between two neurons, in response to the temporal correlation of local presynaptic and postsynaptic signals. These morphological factors are in turn sculpted by the dynamics of the actin cytoskeleton. In this paper, we use Dynamical Graph Grammars (DGGs) implemented within a computer algebra system to model how networks of actin filaments can dynamically grow or shrink, reshaping the spine head. Dynamical Graph Grammars (DGGs) provide a well-defined way to accommodate dynamically changing system structure such as active cytoskeleton represented using dynamic graphs, within nonequilibrium statistical physics under the master equation. We show that DGGs can also incorporate biophysical forces between graph-connected objects at a finer time scale, with specialized DGG kinetic rules obeying biophysical constraints of Galilean invariance, conservation of momentum, and dissipation of conserved global energy. We use graph-local energy functions for cytoskeleton networks interacting with membranes, and derive DGG rules from the specialization of dissipative stochastic dynamics - separated into dissipative and thermal noise rule types - to a mutually exclusive and exhaustive collection of graph-local neighborhood types for the rule left hand sides. The dissipative rules comprise a stochastic version of gradient descent dynamics. The thermal noise rules use a Gaussian approximation of each position coordinate to sample jitter-like displacements. For the spine head model we designed and implemented DGG grammar mathematical sub-models including actin network growth, non-equilibrium statistical mechanics, and filament-membrane mechanical interaction to regulate the re-writing of graph objects. We simulate emergent biophysics of simplified networks of actin polymers and their interactions

关键词： Stochastic models

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The evolution of lithium-ion battery recycling

Nature Reviews Clean Technology

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Nature Reviews Clean Technology 2025年第1期1卷

作者： Xiaotu Ma Zifei Meng Yan Wang Marilena Velonia Bellonia Jeffrey Spangenberger Gavin Harper Eric Gratz Elsa Olivetti Renata Arsenault Mechanical and Materials Engineering Department Worcester Polytechnic Institute Worcester MA USA Technology and Policy Program Institute for Data Systems and Society Massachusetts Institute of Technology Cambridge MA USA ReCell Center Argonne National Laboratory Lemont IL USA School of Metallurgy and Materials University of Birmingham Birmingham UK The Faraday Institution Harwell Science and Innovation Campus Didcot UK Ascend Elements Inc. Westborough MA USA Department of Materials Science and Engineering Massachusetts Institute of Technology Cambridge MA USA Ford Ion Park Battery Center of Excellence Romulus MI USA

Demand for lithium-ion batteries (LIBs) is increasing owing to the expanding use of electrical vehicles and stationary energy storage. Efficient and closed-loop battery recycling strategies are therefore needed, which will require recovering materials from spent LIBs and reintegrating them into new batteries. In this Review, we outline the current state of LIB recycling, evaluating industrial and developing technologies. Among industrial technologies, pyrometallurgy can be broadly applied to diverse electrode materials but requires operating temperatures of over 1,000 °C and therefore has high energy consumption. Hydrometallurgy can be performed at temperatures below 200 °C and has material recovery rates of up to 93% for lithium, nickel and cobalt, but it produces large amounts of wastewater. Developing technologies such as direct recycling and upcycling aim to increase the efficiency of LIB recycling and rely on improved pretreatment processes with automated disassembly and cleaner mechanical separation. Additionally, the range of materials recovered from spent LIBs is expanding from the cathode materials recycled with established methods to include anode materials, electrolytes, binders, separators and current collectors. Achieving an efficient recycling ecosystem will require collaboration between recyclers, battery manufacturers and electric vehicle manufacturers to aid the design and automation of battery disassembly lines.

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Effect of axial heat conduction and internal heat generation on the effectiveness of counter flow microchannel heat exchangers

Effect of axial heat conduction and internal heat generation...

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作者： Mathew, B. Hegab, H. College of Engineering and Science Louisiana Tech University Ruston LA 71272 United States Micro and Nano Systems Track College of Engineering and Science LA Tech. Ruston LA 71272 United States Mechanical Engineering Program College of Engineering and Science LA Tech. Ruston LA 71272 United States

ISBN: (纸本)9781600867453

The influence of axial heat conduction and internal heat generation (viscous dissipation) on the effectiveness of a counter flow microchannel heat exchanger is analyzed in this paper. The ends of the wall separating the hot and cold fluid are kept isothermal, i.e. non-adiabatic, thereby leading to thermal interaction between the heat exchanger and its surroundings. A thermal model of this particular heat exchanger consists of three one dimensional governing equations. This system of equations is solved using finite difference method. The hot and cold fluid effectiveness is found to depend on parameters such as NTU, axial heat conduction parameter, end wall temperatures and internal heat generation parameter. Increase in axial heat conduction parameter of a heat exchanger subjected internal heat generation can either increase or decrease the effectiveness of the fluids depending on the temperature of the end walls. The effect of internal heat generation in a counter flow microchannel heat exchanger with axial heat conduction is to always degrade and improve the effectiveness of the hot and cold fluid, respectively. © 2010 by the American Institute of Aeronautics and Astronautics, Inc.

关键词： Heat exchangers

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Parallel flow microchannel heat exchangers subjected to axial heat conduction and internal heat generation

Parallel flow microchannel heat exchangers subjected to axia...

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ISBN: (纸本)9781600867453

This paper studies the effect of axial heat conduction and internal heat generation (viscous dissipation) on the effectiveness of a parallel flow microchannel heat exchanger. The ends of the wall separating the fluids are maintained at constant temperatures. This leads to heat transfer between the heat exchanger and its surroundings. The thermal model developed in this paper consists of three governing equations;one for each of the fluids and one for the wall. This system of coupled equations is solved simultaneously using finite difference method. The effectiveness of the fluids is found to depend on NTU, axial heat conduction parameter, end wall temperatures and internal heat generation parameter. In the presence of just internal heat generation the effectiveness of the hot and cold fluid degrades and improves, respectively. For situations when the temperature of the end wall at the inlet side is greater than that at the outlet side, increase in axial heat conduction parameter of a heat exchanger subjected internal heat generation increases and decreases the effectiveness of the hot and cold fluid, respectively. The effect of internal heat generation in a parallel flow microchannel heat exchanger with axial heat conduction is to always degrade and improve the effectiveness of the hot and cold fluid, respectively. © 2010 by the American Institute of Aeronautics and Astronautics, Inc.

关键词： Heat exchangers

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Dynamics of fluid flow in a heated zig-zag square microchannel

Dynamics of fluid flow in a heated zig-zag square microchann...

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作者： Mathew, B. John, T.J. Hegab, H. College of Engineering and Science Louisiana Tech University Ruston LA 71272 United States Micro and Nano Systems Track College of Engineering and Science LA Tech. Ruston LA 71272 United States Mechanical Engineering Program College of Engineering and Science LA Tech. Ruston LA 71272 United States

ISBN: (纸本)9781600867453

This paper deals with the dynamics of flow in a zig-zag square microchannel subjected to uniform external heat flux (H2 thermal boundary condition). The heat transfer and fluid flow characteristics is studied using CoventorWare™. Numerical studies are performed using microchannels with hydraulic diameter ranging from 100 μm to 300 μm for Reynolds number between 25 and 500. The angle which each arm of the zig-azg microchannel makes with the axial direction is varied from between 10° and 30° with increments of 10°. The effect of number of turns in a repeating unit for a specific length of the microchannel is also investigated in this paper. The Nusselt number and Poiseuille number in a zig-zag microchannel is found to be totally different from that in a straight square microchannel of the same geometric dimensions. These two parameters are found to increase with increase in Re for zig-zag microchannels with fixed geometry. The individual effect of each of these parameters is to increase both Nusselt number and Poiseuille number for a specific Reynolds number. The enhancement is highest with increase in number of turns while it is the lowest with increase in hydraulic diameter. The enhancement in Nusselt number and Poiseuille number is explained using the flow profile in the microchannels. © 2010 by the American Institute of Aeronautics and Astronautics, Inc.

关键词： Microchannels

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Micro channel heat sink with embedded pin-fin structures

Micro channel heat sink with embedded pin-fin structures

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作者： John, T.J. Mathew, B. Hegab, H. College of Engineering and Science Louisiana Tech University Ruston LA 71272 United States Micro and Nano Systems Track College of Engineering and Science LA Tech. Ruston LA 71272 United States Mechanical Engineering Program College of Engineering and Science LA Tech. Ruston LA 71272 United States

ISBN: (纸本)9781600867453

The dissipation of heat with the help of micro channel heat sink and micro pin-fin fin heat sink has been a topic of interest for many researchers over a decade. The comparison between these two heat sink and the advantage and disadvantages of one over the other has been studied by researchers. In this paper, the authors are trying to study the effect of introducing pin-fin structures inside the micro channel heat sink. A FOM term is introduced in the paper to evaluate the overall performance of the ordinary micro channel heat sink and the micro channel heat sink with pin-fin structures embedded in it. The effect of introducing different shapes of pin-fin structures inside the micro channel is also studied in the paper. The study results showed that there is a huge increase in the overall performance of the micro channel heat sink by introducing pin-fin structures inside the channel, but the study also showed that the effect of introducing different shapes of pin-fin structures inside the channel is negligible. © 2010 by the American Institute of Aeronautics and Astronautics, Inc.

关键词： Fins (heat exchange)

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Improvement of transmittance by fabricating broadband subwavelength anti-reflection structures for polycarbonate

Improvement of transmittance by fabricating broadband subwav...

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作者： Jang, H.S. Kim, J.H. Kim, K.S. Jung, G.Y. Lee, J.J. Kim, G.H. Division of Nano and Bio Technology Daegu-Gyeongbuk Institute of Science and Technology Dalseo-gu Daegu 704-230 Korea Republic of Department of Material Science and Engineering Program for Integrated Molecular System Gwangju Institute of Science and Technology Gwangju 500-712 Korea Republic of Nano-Mechanical Systems Research Division Korea Institute of Machinery and Materials Daejeon 305-343 Korea Republic of

We report on how to increase transmittance of a 0.2 mm thick polycarbonate (PC) film by periodic subwavelength anti-reflection structures in the visible spectral range. Subwavelength anti-reflection structures like moth-eyes are fabricated into the polycarbonate substrate itself by thermal nanoimprinting lithography (TH-NIL), which uses silicon stamps that have periodic structures such as gratings (lines and spaces) and pillared dots, and are fabricated by laser interference lithography (LIL) and transformer coupled plasma etching. To increase transmittance of a polycarbonate film, we control the periods and shapes of patterns, the number of patterned surfaces, and the overlapping direction of patterns that are fabricated into its surfaces. As a result of this, we show that average transmittance improves as the pattern period gets shorter and as both surfaces of the film are patterned. We also show that the spectrum range gets larger as the pattern period gets shorter and is determined by the longer pattern period in the case of designing a film to have different pattern period on its surfaces. The maximum average transmittance of a polycarbonate film increases up to approximately 6% compared to a bare sample in the 470-800 nm spectral range. Copyright © 2011 American Scientific Publishers All rights reserved.

关键词： Polycarbonates

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A robotic and virtual testing platform highlighting the promise of soft wearable actuators for wrist tremor suppression

Device

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Device 2025年

作者： Alona Shagan Shomron Christina Chase-Markopoulou Johannes R. Walter Johanna Sellhorn-Timm Yitian Shao Tobias Nadler Audrey Benson Isabell Wochner Ellen H. Rumley Isabel Wurster Philipp Klocke Daniel Weiss Syn Schmitt Christoph Keplinger Daniel F.B. Haeufle Robotic Materials Department Max Planck Institute for Intelligent Systems Stuttgart Germany Institute for Modelling and Simulation of Biomechanical Systems University of Stuttgart Stuttgart Germany Stuttgart Center for Simulation Science (SimTech) University of Stuttgart Stuttgart Germany Hertie Institute for Clinical Brain Research University of Tübingen Tübingen Germany Haptic Intelligence Department Max Planck Institute for Intelligent Systems Stuttgart Germany Institute for Computer Engineering (ZITI) University of Heidelberg Heidelberg Germany Paul M. Rady Department of Mechanical Engineering University of Colorado Boulder CO USA Center for Neurology Department of Neurodegenerative Diseases University of Tübingen Tübingen Germany Center for Bionic Intelligence (BITS) Tübingen and Stuttgart Germany Material Science and Engineering Program University of Colorado Boulder CO USA Werner Reichardt Center for Integrative Neuroscience University of Tübingen Tübingen Germany

Nearly 80 million people in the world deal with medical conditions that cause involuntary periodic movements known as tremors. Wearable soft robotic devices offer a potential solution for actively suppressing these tremors. However, existing prototypes face limitations in actuation performance and complex testing procedures. We present a comprehensive approach for the rapid evaluation of emerging wearable tremor-suppression technologies. This method combines reproducing patient-recorded tremor episodes and measuring tremor suppression in a robotic platform, termed a “mechanical patient”, with validation of the achieved suppression performance of soft actuators via biomechanical modeling, thereby avoiding time-consuming clinical testing in the early stages of development. Using this approach, we highlight that an antagonistic pair of slim and lightweight electrohydraulic actuators can effectively suppress clinically relevant tremors between 2 and 8 Hz. The biomechanical model confirms that the pair of actuators generates adequate suppression forces for all tested tremors.

关键词： tremor suppression mechanical patient soft actuators wearable devices biomechanical simulation DTI-4: Validate

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Hardware particle swarm optimization based on the attractive-repulsive scheme for embedded applications

Hardware particle swarm optimization based on the attractive...

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2010 International Conference on Reconfigurable Computing and FPGAs, ReConFig 2010

作者： Muñoz, Daniel M. Llanos, Carlos H. Dos S. Coelho, Leandro Ayala-Rincón, Mauricio Department of Mechanical Engineering Automation and Control Group/GRACO University of Brasilia Brasilia DF Brazil Industrial and Systems Engineering Graduate Program LAS/PPGPES Pontifical Catholic University of Parana Curitiba Parana Brazil Department of Computer Science and Mathematics University of Brasilia Brasilia DF Brazil

ISBN: (纸本)9780769543147

Particle Swarm Optimization (PSO) algorithms have been proposed to solve engineering problems that require to find an optimal point of operation. However, the PSO algorithm suffers from premature convergence and high elapsed time when solving multimodal and large scale engineering problems. This problem becomes an evident drawback for embedded applications in which the microcontrollers often operates at low computational capacity. This paper proposes a hardware implementation of a parallel self-adaptive PSO algorithm based on an attractive-repulsive scheme and using the efficient floating-point arithmetic which performs computations with large dynamic range and high precision. The parallel capabilities of the PSO are exploited by implementing parallel particles directly in hardware in order to decrease the running time. In addition, the attractive-repulsive technique avoids the premature convergence problem by self-adapting the swarm behavior according to its diversity. Synthesis and simulation results for benchmark test problems were performed, demonstrating the correctness of the proposed architectures. Finally, an elapsed time comparison between the hardware and software implementations shows the suitableness of the proposed architecture for embedded applications. © 2010 IEEE.

关键词： Global optimization

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Variable-Speed Teaching-Playback as Real-World Data Augmentation for Imitation Learning

arXiv

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arXiv 2024年

作者： Masuya, Nozomu Sato, Hiroshi Yamane, Koki Kusume, Takuya Sakaino, Sho Tsuji, Toshiaki Master's Program in Intelligent and Mechanical Interaction Systems Degree Programs in Systems and Information and Engineering Graduate School of Science and Technology University of Tsukuba Japan Doctoral Program in Intelligent and Mechanical Interaction Systems Degree Programs in Systems and Information and Engineering Graduate School of Science and Technology University of Tsukuba Japan Department of Intelligent Interaction Technologies Institute of Systems and Information Engineering University of Tsukuba Japan Graduate School of Science and Engineering Saitama University Saitama Japan

Because imitation learning relies on human demonstrations in hard-to-simulate settings, the inclusion of force control in this method has resulted in a shortage of training data, even with a simple change in speed. Although the field of data augmentation has addressed the lack of data, conventional methods of data augmentation for robot manipulation are limited to simulation-based methods or downsampling for position control. This paper proposes a novel method of data augmentation that is applicable to force control and preserves the advantages of real-world datasets. We applied teaching-playback at variable speeds as real-world data augmentation to increase both the quantity and quality of environmental reactions at variable speeds. An experiment was conducted on bilateral control-based imitation learning using a method of imitation learning equipped with position-force control. We evaluated the effect of real-world data augmentation on two tasks, pick-and-place and wiping, at variable speeds, each from two human demonstrations at fixed speed. The results showed a maximum 55% increase in success rate from a simple change in speed of real-world reactions and improved accuracy along the duration/frequency command by gathering environmental reactions at variable speeds. Copyright © 2024, The Authors. All rights reserved.

关键词： Demonstrations

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