499 research outputs found
Artificial Synapses with Short- and Long-Term Memory for Spiking Neural Networks Based on Renewable Materials
No full textEmulation of biological synapses that perform memory and learning functions is an essential step toward realization of bioinspired neuromorphic systems. Artificial synaptic devices have been developed based mostly on inorganic materials and conventional semiconductor device fabrication processes. Here, we propose flexible biomemristor devices based on lignin by a simple solution process. Lignin is one of the most abundant organic polymers on Earth and is biocompatible, biodegradable, as well as environmentally benign. This memristor emulates several essential synaptic behaviors, including analog memory switching, short-term plasticity, long-term plasticity, spike-rate-dependent plasticity, and short-term to long-term transition. A flexible lignin-based artificial synapse device can be operated without noticeable degradation under mechanical bending test. These results suggest lignin can be a promising key component for artificial synapses and flexible electronic devices.1131sciescopu
Damage Detection of Composite Structures using Full-Field Pulse-Echo Ultrasonic Propagation Imaging System
No full textIn-progress & In-assembly NDE of Composite Space Launcher Structures using Bulk Wave Ultrasonic Propagation Imaging
No full textComposite Zero-Effort-Miss Guidance with Predictor–Corrector Steps for Ballistic Interception
No full text<jats:p> In this paper, a midcourse guidance law for exoatmospheric interception using a solid-propellant rocket is presented. Existing guidance laws based on the zero-effort-miss concept lack consideration for remaining thrust, potentially resulting in the excessive magnitude and rate of the thrust direction command. To address this issue, the zero-effort-miss concept is combined with an iterative predictor–corrector-based guidance law that is adapted for solid-propellant rockets. To apply the iterative predictor–corrector-based guidance law to the interception problem with a solid-propellant rocket, a composite zero-effort-miss concept is introduced, and the correction step is formulated as an online convex optimization problem. The composite zero-effort-miss consists of two zero-effort-misses. One miss is obtained from current state and the other miss is obtained from predicted state at burnout. Those render the proposed guidance law robust to thrust uncertainty allow for a noniterative approach and eliminate the singularity problem. Also, the proposed guidance law reduces maneuvering during the early part of the midcourse phase, leading to less velocity loss, and resolves intercept performance degradation due to the rate limit of thrust vectoring. Numerical simulations comparing the proposed method with the modified zero-effort-miss guidance demonstrate its effectiveness and robustness. </jats:p>
Flexible Artificial Synaptic Devices Based on Collagen from Fish Protein with Spike-Timing-Dependent Plasticity
No full textNeuromorphic and cognitive computing with a capability of analyzing complicated information is explored as a new paradigm of intelligent systems. An implementation of a renewable material as an essential building block of an artificial synaptic device is suggested and a flexible and transparent synaptic device based on collagen extracted from fish skin is demonstrated. This device exhibits essential synaptic behaviors including analog memory characteristics, excitatory postsynaptic current, and paired-pulse facilitation as short-term plasticity. The brain-inspired electronic synapse undergoes incremental potentiation and depression when flat or bent. The device emulates spike-timing-dependent plasticity when stimulated by engineered pre- and post-neuron spikes with the appropriate time difference between the imposed pulses. The proposed synaptic device has the advantage of being biocompatible owing to use of Mg electrodes and collagen as a naturally abundant protein. This device has a potential to be used in flexible and implantable neuromorphic systems in the future.11sciescopu
Reduced Graphene Oxide-Based Artificial Synapse Yarns for Wearable Textile Device Applications
No full textA brain-inspired neuromorphic system is a promising computing concept that processes information at low power. Such systems can be applied to wearable devices in which low power consumption is important. Solid-state devices that have been used for neuromorphic device applications are not suitable for wearable applications that require high flexibility. Here, two-terminal memristor-based artificial synapses are proposed that are simply constructed by crossing two yarns coated with reduced graphene oxide (RGO) by electrochemical deposition. The artificial synapses mimic several important synaptic functions of biological synapses, including excitatory postsynaptic current, paired-pulse facilitation, and a transition from short-term plasticity to long-term plasticity. The artificial synapses can be operated stably without degradation during mechanical bending. By implementing a 2 x 2 cross-point array using RGO-coated yarns, the possibility of integrating artificial synapses for wearable neuromorphic systems is demonstrated. The yarn-based artificial synapses can be a key component of future neuromorphic wearable systems.11sciescopu
Advanced Neural Interface toward Bioelectronic Medicine Enabled by Micro-Patterned Shape Memory Polymer
Full text linkRecently, methods for the treatment of chronic diseases and disorders through the modulation of peripheral and autonomic nerves have been proposed. To investigate various treatment methods and results, experiments are being conducted on animals such as rabbits and rat. However the diameter of the targeted nerves is small (several hundred μm) and it is difficult to modulate small nerves. Therefore, a neural interface that is stable, easy to implant into small nerves, and is biocompatible is required. Here, to develop an advanced neural interface, a thiol-ene/acrylate-based shape memory polymer (SMP) was fabricated with a double clip design. This micro-patterned design is able to be implanted on a small branch of the sciatic nerve, as well as the parasympathetic pelvic nerve, using the shape memory effect (SME) near body temperature. Additionally, the IrO2 coated neural interface was implanted on the common peroneal nerve in order to perform electrical stimulation and electroneurography (ENG) recording. The results demonstrate that the proposed neural interface can be used for the modulation of the peripheral nerve, including the autonomic nerve, towards bioelectronic medicine
Cost-effective TSV redundancy configuration
No full textDespite of distinct benefits, such as small form factor, low power consumption, and high performance, the high fabrication cost from both low yield and large area of through-silicon-via (TSV) still keeps three-dimensional integrated circuit (3D IC) from being commercialized in the industry. Inserting additional TSVs (i.e., TSV redundancy) is a well-known solution to increase fabrication yield of 3D IC. However, considering the significant overhead of TSV redundancy, a design-time optimization process is required to find cost-minimal TSV redundancy configuration. In this paper, we proposed a fabrication cost model for 3D IC which takes the TSV redundancy configuration into account. The analytical cost model has been explored with various number of TSVs, to find cost-minimal TSV redundancy configuration. We have also investigated fabrication cost of 3D IC with respect to the failure rate of TSV itself, which show a trend of fabrication cost for future TSV technology
Solution-Processed Flexible Threshold Switch Devices
No full textFlexible threshold switch devices are essential for low-power and high-speed semiconductor devices. Especially, bidirectional threshold switch has been regarded as the ideal switching device for ultrahigh-density crosspoint memory devices. Here, a flexible Pt/Ag-doped ZnO/Pt switch on the flexible plastic substrate synthesized by electrochemical bottom-up deposition is introduced. The flexible switch has bidirectional threshold switching behavior with ultralow off-current, high selectivity (approximate to 10(7)), and super-steep threshold slope. The bidirectional threshold switching behavior is related to migration of silver ions to form Ag filament. This device shows stable electrical properties, endures constant voltage stress, and retains good reliability under mechanical stress. It is believed that this study would open up new possibilities for high-density flexible memory devices by introducing flexible novel bidirectional, high-performance switching devices for emerging flexible electronics.114sciescopu
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