Molecular dynamics simulations of nanoclusters in neuromorphic systems

Neuromorphic computing is a new computing paradigm that deals with computing tasks using inter-connected artificial neurons inspired by the natural neurons in the human brain. This computational architecture is more efficient in performing many complex tasks such a pattern recognition and has promise at overcoming some of the limitations of conventional computers. Among the emerging types of artificial neurons, a cluster-based neuromorphic device is a promising system with good costefficiency because of a simple fabrication process. This device functions using the formation and breakage of the connections (“synapses”) between clusters, driven by the bias voltage applied to the clusters. The mechanisms of the formation and breakage of these connections are thus of the utmost interest. In this thesis, the molecular dynamics simulation method is used to explore the mechanisms of the formation and breakage of the connections (“filaments”) between the clusters in a model of neuromorphic device. First, the Joule heating mechanism of filament breakage is explored using a model consisting of Au nanowire that connects two Au1415 clusters. Upon heating, the atoms of the nanofilament gradually aggregate towards the clusters, causing the middle of the wire to graduallythin and then suddenly break. Most of the system remains crystalline during this process, but the centre becomes molten. The terminal clusters increase the melting point of the nanowires by fixing them and act as recrystallisation regions. A strong dependence of the breaking temperature is found not only on the width of the nanowires but also their length and atomic structure. Secondly, the bridge formation and thermal breaking processes between Au1415 clusters on a graphite substrate are also simulated. The bridging process , which can heal a broken filament, is driven by diffusion of gold along the graphite substrate. The characteristic times of bridge formation are explored at elevated simulation temperatures to estimate the longer characteristic times of formation at room-temperature conditions. The width of the bridge formed has a power-law dependence on the simulation time, and the mechanism is a combination of diffusion and viscous flow. Simulations of bridgebreaking are also conducted and reveal the existence of a voltage threshold that must be reached to activate the breakage. The role of the substrate in the bridge formation and breakage processes is revealed as a medium of diffusion. Lastly, to explore future potential cluster materials, the thermal behaviour of Pb-Al core-shell clusters is studied. The core and shell are found to melt separately. In fact, the core atoms of nanoclusters tend to escape their shells and partially cover them, leading to a preference for a segregated state. The melting point of the core can either be depressed or elevated, depending on the thickness of the shell due to different mechanisms

Energy Transfer Concept in AC/DC Switch Mode Power Supply with Power Factor Correction

A new innovative concept in AC/DC converter that transfers energy to the output side directly from the input line, rather than from the storage capacitor in power factor correction (PFC) cell during the line voltage exceeds the present value. The new concept is based on providing additional winding coupled to the DC/DC transformer connected to the rectified input side to provide a path for the energy transfer from the line to transfer to the output directly (Boost converter) or to be stored in the output transformer Flyback cell)

Design of magnetic coupling of continuous wave of measurement while drilling

According to the special working environment of drilling proposed design parameters of distance sleeve; The Ansoft Maxwell software is used to optimize the magnetic coupling, and the optimized design process is illustrated with an example; The torque is studied under different rotation angles; The effects of magnetic steel thickness, magnet thickness and magnetic pole number on torque are studied respectively; With the development of the rare earth permanent magnet material, it is imperative to apply the no leakage magnetic coupling to petroleum drilling

Mapping nanoarchitecture of liquid-gel-solid interfaces : 3D nano-rheology microscopy nanoprobing from molecular layers to volume reconstruction

One of the largest challenges for scanning probe microscopy (SPM) is exploiting its superior nanoscale to atomic resolution and SPM ability work in vacuum, air and liquid environments beyond the immediate surface of the sample. A particular challenge is to study the soft matter surfaces (such as living cells or bacteria, polymer brushes or electrolyte-electrode interfaces in batteries) where the interfaces are not well defined and structures are truly three-dimensional. Here, we report novel 3D nano-rheology microscopy (3D-NRM) that uses a tiny (sub-nm to few nm) lateral dithering of the sharp SPM tip at kHz frequencies to probe the minute sample reaction forces. By mapping the increments of the real and imaginary components of these forces, while penetrating the soft interfacial layers, we obtain the true 3D nanoscale structure of sub–m thick layers [1]. By combining 3D-NRM with the surface force-distance spectroscopy [2] (Fig 1d) in the operando electrochemical environment, we observed for the first time in real space the nanoscale dynamics of formation of the key solid electrolyte interphase (SEI) layer in Li-ion batteries starting from a few 0.1 nm thick electrical double layer to the full 3D nanostructured SEI (Fig 1e). We therefore were able to elucidate the key role of solvents in such formation and predict the conditions for building SEI for robust, safe and efficient Li-ion batteries. The new 3D-NRM can provide unique opportunity for studies inorganic catalytic and separation processes, to explore biological interfaces probing bacterial and cell surfaces, and functional coating in the real space and appropriate operational environment