Order Of Watts Research Articles

Theoretical demonstration of a capacitive rotor for generation of alternating current from mechanical motion

Innovative concepts and materials are enabling energy harvesters for slower motion, particularly for personal wearables or portable small-scale applications, hence contributing to a future sustainable economy. Here we propose a principle for a capacitive rotor device and analyze its operation. This device is based on a rotor containing many capacitors in parallel. The rotation of the rotor causes periodic capacitance changes and, when connected to a reservoir-of-charge capacitor, induces alternating current. The properties of this device depend on the lubricating liquid situated between the capacitor’s electrodes, be it a highly polar liquid, organic electrolyte, or ionic liquid – we consider all these scenarios. An advantage of the capacitive rotor is its scalability. Such a lightweight device, weighing tens of grams, can be implemented in a shoe sole, generating a significant power output of the order of Watts. Scaled up, such systems can be used in portable wind or water turbines.

A low-power, jamming, magnetorheological valve using electropermanent magnets suitable for distributed control in soft robots

Magnetorheological (MR) valves are an attractive way to make reliable valves with no moving parts. MR fluid valves operate by powering an electromagnet positioned near a constriction through which MR fluid is flowing. However, these valves are high-power devices, consuming on the order of watts of power while closed, and the electromagnets and flow paths are relatively bulky. Due to their power draw and size, they are unsuitable for many miniaturized and portable applications which would otherwise benefit from a solid state valve. In this paper, we introduce a low power, jamming MR valve that makes use of an electropermanent magnet, which can provide either a strong magnetic field or no field, with no continuous power draw and no moving parts. The resulting valve has overall dimensions of 4× 4×6mm, a mass of 0.476g, material costs of $7.32 per valve USD at quantity 100, holds over 415 kPa of pressure, and leaks only 0.02g of fluid over a 24h period when held at 105 kPa. These valves are well suited for use in soft robots, e.g. robots composed of stretchable elastomers and may allow for increased degrees of freedom in soft robotic designs. We discuss the design considerations for making MR valves, study the effect of different fluids and valve sizes, develop a numerical framework for simulation and further valve design, and demonstrate the use of a MR valve to control the actuation of a soft robotic appendage.

Deep compressive autoencoder for action potential compression in large-scale neural recording

Objective. Understanding the coordinated activity underlying brain computations requires large-scale, simultaneous recordings from distributed neuronal structures at a cellular-level resolution. One major hurdle to design high-bandwidth, high-precision, large-scale neural interfaces lies in the formidable data streams (tens to hundreds of Gbps) that are generated by the recorder chip and need to be online transferred to a remote computer. The data rates can require hundreds to thousands of I/O pads on the recorder chip and power consumption on the order of Watts for data streaming alone. One of the solutions is to reduce the bandwidth of neural signals before transmission. Approach. We developed a deep learning-based compression model to reduce the data rate of multichannel action potentials. The proposed compression model is built upon a deep compressive autoencoder (CAE) with discrete latent embeddings. The encoder network of CAE is equipped with residual transformations to extract representative features from spikes, which are mapped into the latent embedding space and updated via vector quantization (VQ). The indexes of VQ codebook are further entropy coded as the compressed signals. The decoder network reconstructs spike waveforms with high quality from the quantized latent embeddings through stacked deconvolution. Main results. Extensive experimental results on both synthetic and in vivo datasets show that the proposed model consistently outperforms conventional methods that utilize hand-crafted features and/or signal-agnostic transformations and compressive sensing by achieving much higher compression ratios (20–500×) and better or comparable reconstruction accuracies. Testing results also indicate that CAE is robust against a diverse range of imperfections, such as waveform variation and spike misalignment, and has minor influence on spike sorting accuracy. Furthermore, we have estimated the hardware cost and real-time performance of CAE and shown that it could support thousands of recording channels simultaneously without excessive power/heat dissipation. Significance. The proposed model can reduce the required data transmission bandwidth in large-scale recording experiments and maintain good signal qualities, which will be helpful to design power-efficient and lightweight wireless neural interfaces. We have open sourced the code implementation of the work at https://github.com/tong-wu-umn/spike-compression-autoencoder.

Enhanced triplet-triplet annihilation in bicomponent organic systems by using a gap plasmon resonator.

The triplet-triplet annihilation (TTA) efficiency in bicomponent organic systems is investigated by employing a gap plasmon resonator. In our structure, strong absorption peaks arising from coupling between localized surface plasmons and surface plasmon polaritons closely overlap the Q band of porphyrin, leading to higher triplet concentrations within the film. We find that at ultralow excitation intensities on the order of watts per square centimeter (W cm(-2)), TTA becomes predominant for the organic system on a gap plasmon resonator. A strong surface-enhanced Raman scattering intensity is observed in this substrate, verifying the near-field enhancement.

Power management system for a 2.5 W remote sensor powered by a sediment microbial fuel cell

One of the challenges in using wireless sensors that require high power to monitor the environment is finding a renewable power source that can produce enough power. Sediment microbial fuel cells (SMFCs) are considered an alternative renewable power source for remote monitoring, but current research on SMFCs has demonstrated that they can only produce several to tens of mW of continuous power. This limits the use of SMFCs as an alternative renewable remote power source to mW-level power. Such low power is only enough to operate a low-power sensors. However, there are many remote sensors that require higher power, on the order of watts. Current technology using a SMFC to power a remote sensor requiring watts-level intermittent power is limited because of limitations of power management technology. Our goal was to develop a power management system (PMS) that enables a SMFC to operate a remote sensor consuming 2.5 W of power. We designed a custom PMS to store microbial energy in capacitors and use the stored energy in short bursts. Our results demonstrate that SMFCs can be a viable alternative renewable power source for remote sensors requiring high power.

Surface Modification of Metallic Targets with Ultrashort Laser Pulses

Interaction of pulsed femtosecond Ti:sapphire laser (160 fs), operating at high repetition rate (75 MHz) at 800 nm, with nickel-based superalloy Inconel 600 and tungsten–titanium (WTi) target was studied. The WTi target was in form of thin film deposited on silicon substrate. Low laser fluence of maximum 50 mJ/cm had modified the target surface during irradiation/exposure time of seconds or minutes. The radiation absorbed from the laser beam generates at the surface a series of effects, such as direct material vaporization, formation of clusters, etc. Morphological features of the targets can be summarized as: (a) intensive removal of material and crater appearance; (b) creation of nanostructures; (c) microcracking, etc. Ablation of Inconel 600 surface is effective, resulting in formation of holes with small diameter (≤ 10 μm) and relatively large depth (≤ 50 μm). In case of WTi target/thin film, the surrounding rim is not so expressed, and crater depths are lower. It can be concluded that the average laser power of the order of watts, pulse energies of the order of nanojoules and high repetition rates (MHz range) can successfully modify metallic materials.

POWER GENERATION AT THE MICRO SCALE

The present work is to show the development of micropower systems or power MEMS characterized by thermal, electrical and mechanical power density 1~20 Watts in sub-centimeter-sized packages. Three kinds of typical micro power systems, namely, the micro-gas turbine engine, the MEMS rotary micro engine, and a micro thermoelectric system, are described in this paper. A novel microthermophotovoltaic (micro-TPV) system, which is being developed in NUS, is also introduced in this work. The system uses hydrogen as fuel and is able to deliver electrical power in the order of watts in a package less than 1 cubic centimeter in volume. The main components of the system are a heat source, a selective emitter, and a photovoltaic (PV) array. The performance of the system is largely affected by the materials of the emitter and the PV cells. When the emitter is made of Co/Ni-doped MgO, and the PV cells are made of GaSb, a 4.4 W electrical power output can be expected.

Research on micro-thermophotovoltaic power generators

Abstract A novel power Micro Electro-Mechanical Systems concept, a micro-thermophotovoltaic (micro-TPV) system, is described in this work. The system uses hydrogen as fuel and is capable of delivering power in the order of watts in a package less than 1 cm 3 in volume. Based on the experimental results of micro-SiC flame tube combustor, emitters (radiators) and photovoltaic cells, a mathematical model is developed to evaluate the performance of the micro-TPV systems. As H 2 flow rate is 3.88 g/h, H 2 /air ratio is 0.95, A 4.40 W electrical power output can be expected in a micro-combustor of 0.113 cm 3 in volume.

3222 ウルトラマイクロガスタービン用動圧型空気軸受の開発

Currently, an ultra-micro gas turbine has been paid attention as attractive MEMS power systems and high-speed micro-rotating machinery was proposed to provide mechanical-to-electrical energy conversion system with the order of watts. This kind of device is usually made of single crystal silicon and the rotor is supported by both aerostatic joumal and thrust bearings. In this paper, a newly developed structure of high speed micro-rotating rotor supported by an aerodynamic joumal bearing instead of an aerostatic bearing is proposed. In addition, the proposed bearing adopts a floating bush to improve the stability at high speeds. The floating bush is supported by an aerostatic bearing using a pressurized air fed by an aerodynamic herringbone grooved joumal bearing. It was found that the proposed bearing was able to generate sufficient pressure to support a floating bush.

Controlling radio frequency interference from neurological prostheses

The simplest kind of radio frequency (RF) coupled neurological prosthesis, in which a burst of RF, generated by the external equipment, provides the stimulus energy via a passive implanted receiver, is the most troublesome in respect of RF interference (RFI). Because the low ratio of pulse duration to interpulse interval is usually the case, the peak power transmitted is necessarily high, of the order of watts. This paper outlines a series of measurements by which the mode of RFI generation by a typical external equipment was precisely identified, enabling rational and appropriate countermeasures to be taken.

Induced emission of radiation from a large space-station-like structure in the ionosphere

Large conducting structures in the ionosphere may have currents flowing through them which close in the ionospheric plasma. These currents can arise either from current leakage from an onboard power distribution system or by being induced by the motional electric field. Associated with these currents will be broadband electromagnetic radiation in the Alfven and lower hybrid bands. The radiation impedance of this electromagnetic radiation is explored for a structure of space-station-like dimensions as a function of the geometry of the structure and the composition of the ionic environment. It is shown that modification of the collecting area of the structure and environment can be used to minimize the radiation impedance. For a space station, the radiated power will at most be of the order of watts, which does not represent a significant power loss. However, the radiation field will give rise to a substantial pollution of the electromagnetic spectrum in the vicinity of the space station. Design choices to minimize this interference are suggested.

Microwave Variable Attenuators and Modulators Using PIN Diodes

The PIN diode is a double diffused junction with an intrinsic layer separating the P and N regions. At frequencies above 100 Mc, the diode ceases to be a rectifier because of carrier storage and transit time effects. Its shunt capacitance is quite small because of the separation of the P and N regions by the I layer. Conductivity of the I region can be varied by a dc bias current and the device becomes an electrically variable resistor which can be used for microwave attenuators and modulators up to frequencies as high as 20 Gc. The PIN junctions are mounted on posts which are inserted in a 50-ohm strip transmission line as shunt elements, and a number of these elements, spaced a quarter wavelength apart at midband, are used to form an attenuator. At the appropriate bias current, yielding 50-ohm junction resistances, the diode elements are reactively compensated by choice of post dimensions so that they are effectively pure resistances, yielding an image attenuation of 4.2 db per element. Many elements can be used to attain any desired total attenuation and higher impedance end elements can be used to improve the SWR. Bandwidths of 4 to 1 with low SWR in both ON and OFF conditions are achievable. Maximum attenuation of 60 db, insertion loss of 1 db, and SWR of 1.5 are typical for a 12-diode attenuator and powers of the order of watts can be handled with negligible harmonic generation. When used as a pulse modulator, rise times of the order of 10 nsec are achievable.