Although the concept of variable-speed drives, based on utilization of multiphase machines, dates back to the late 1960s, it was not until the mid- to late 1990s that multiphase drives became serious contenders for various applications. These include electric ship propulsion, locomotive traction, electric and hybrid electric vehicles, ldquomore-electricrdquo aircraft, and high-power industrial applications. As a consequence, there has been a substantial increase in the interest for such drive systems worldwide, resulting in a huge volume of work published during the last ten years. An attempt is made in this paper to provide a brief review of the current state of the art in the area. After addressing the reasons for potential use of multiphase rather than three-phase drives and the available approaches to multiphase machine designs, various control schemes are surveyed. This is followed by a discussion of the multiphase voltage source inverter control. Various possibilities for the use of additional degrees of freedom that exist in multiphase machines are further elaborated. Finally, multiphase machine applications in electric energy generation are addressed.

Multiphase Electric Machines for Variable-Speed Applications

Electron transport experiments on two lateral quantum dots coupled in series are reviewed. An introduction to the charge stability diagram is given in terms of the electrochemical potentials of both dots. Resonant tunneling experiments show that the double dot geometry allows for an accurate determination of the intrinsic lifetime of discrete energy states in quantum dots. The evolution of discrete energy levels in magnetic field is studied. The resolution allows one to resolve avoided crossings in the spectrum of a quantum dot. With microwave spectroscopy it is possible to probe the transition from ionic bonding (for weak interdot tunnel coupling) to covalent bonding (for strong interdot tunnel coupling) in a double dot artificial molecule. This review is motivated by the relevance of double quantum dot studies for realizing solid state quantum bits.

/pdf/electron-transport-through-double-quantum-dots-ppsjj6z4lk.pdf

Electron transport through double quantum dots

The goal of this paper is to review in brief the basic physics of single-election devices, as well as their-current and prospective applications. These devices based on the controllable transfer of single electrons between small conducting "islands", have already enabled several important scientific experiments. Several other applications of analog single-election devices in unique scientific instrumentation and metrology seem quite feasible. On the other hand, the prospect of silicon transistors being replaced by single-electron devices in integrated digital circuits faces tough challenges and remains uncertain. Nevertheless, even if this replacement does not happen, single electronics will continue to play an important role by shedding light on the fundamental size limitations of new electronic devices. Moreover, recent research in this field has generated some by-product ideas which may revolutionize random-access-memory and digital-data-storage technologies.

Single-electron devices and their applications

Advanced Mathematical Methods for Scientists and Engineers

The investigation of the conversion of vibrational energy into electrical power has become a major field of research. In recent years, bistable energy harvesting devices have attracted significant attention due to some of their unique features. Through a snap-through action, bistable systems transition from one stable state to the other, which could cause large amplitude motion and dramatically increase power generation. Due to their nonlinear characteristics, such devices may be effective across a broad-frequency bandwidth. Consequently, a rapid engagement of research has been undertaken to understand bistable electromechanical dynamics and to utilize the insight for the development of improved designs. This paper reviews, consolidates, and reports on the major efforts and findings documented in the literature. A common analytical framework for bistable electromechanical dynamics is presented, the principal results are provided, the wide variety of bistable energy harvesters are described, and some remaining challenges and proposed solutions are summarized.

https://iopscience.iop.org/article/10.1088/0964-1726/22/2/023001/pdf

A review of the recent research on vibration energy harvesting via bistable systems

This paper presents a microfabricated electro-quasi-static (EQS) induction turbine generator that has generated net electric power A maximum power output of 192 muW was achieved under driven excitation We believe that this is the first report of net-electric-power generation by an EQS induction machine of any scale found in the open literature This paper also presents self-excited operation in which the generator resonates with an inductor and generates power without the use of external active-drive electronics The generator comprises five silicon layers, fusion-bonded together at 700degC The stator is a platinum-electrode structure formed on a thick (approximately 20 mum) recessed oxide island The rotor is a thin film of lightly doped polysilicon also residing on a 10-mum-thick oxide island Carrier depletion in the rotor conductor film limited the performance of the generator This paper also presents a generalized state-space model for an EQS induction machine that takes into account the machine and its external electronics and parasitics This model correlates well with measured performance and was used to find the optimal drive conditions for all driven experiments

A Self-Excited MEMS Electro-Quasi-Static Induction Turbine Generator

This paper presents quantitative modeling and characterization of the initial assembly process that takes place during templated assembly by selective removal (TASR). The present model complements the earlier analytical treatment of TASR, which only described TASR's selective removal process. The model describes how the geometry of and interactions between the components and assembly substrate, along with the mean fluid flows, predict the circumstances under which fluid effects will successfully drive initial placement of components into the assembly sites. Experiments that confirm the model predictions are presented. These results are used to identify how scaling trends affect the effectiveness of TASR's initial assembly and selective removal processes.

Modeling and Characterizing Initial Component Assembly in Templated Assembly by Selective Removal

This paper presents the design and experimental characterization of a compact parallel-beam architecture for low-frequency energy harvesters that switch passively among dynamical modes to extend their operational range. Two beams interact to generate power; a driving beam couples into low frequency vibrations, and a higher frequency generating beam outputs power upon impact by the driving beam. The system switches between modes in which the driving beam bounces off the generating beam (coupled motion) and modes in which the driving beam passes the generating beam (plucked motion). The compact structure is realized by mounting the generating beam within a U-shaped driving beam on a single support. A flexible tip is mounted inside the driving beam's U shape to enable robust interactions. This new architecture reduces system volume by 80% compared with an earlier model that has the same resonance frequency, but it also changes the flexible tip's role in the contact dynamics. The flexible tip is experimentally tailored to optimize performance. The harvester generates power over the measured range of acceleration from 0.2 g to 2 g and driving frequency from 5 Hz to 20 Hz. With one tip design, the harvester offers peak power of 0.267 mW with plucked operation covering 32% of the tested range. With a second tip design, the harvester offers a lower peak power of 0.036 mW with plucked operation covering 73% of the tested range.

A compact architecture for passively-switched energy harvesters

The design, modeling, fabrication and successful demonstration of a bulk-micromachined MEMS valve that enables high gas flow rates of hundreds of sccm in its initial open state and ultra low-leak, permanent sealing against gas flow once closed are demonstrated. When the valve is open, a high aspect ratio ring of solder surrounds its flow orifice without blocking the flow path. When the valve is thermally actuated by an integrated resistive heater, the solder melts and reflows, creating an irreversible seal over the flow orifice. The flow orifice is formed in a silicon 'island' that is supported on a thermally-insulating membrane to limit heat conduction to the surrounding silicon and to minimize the input power that is needed to close the valve. The valve's measured open flow rate is up to approximately 400 sccm. The flow orifice is observed to seal when about 0.3 W of power are input to the resistive heater. To within the measurement uncertainty, the measured leak rate during valve testing is comparable to the measured leak rate when flow is measured through a solid plate, indicating that the valve's leakage is less than the test system's parasitic leakage and outgassing. The minimum, average, and maximum values of difference between the valve leak rate and the system's parasitic leak rate are 0 sccm, 0.65 × 10–4 sccm, and 1.65 × 10–4 sccm respectively when a 1 atmosphere pressure difference is applied across the valve. The average value corresponds to an open-to-closed flow rate ratio of greater than 6 × 106. This compact sealing valve may be combined with low and high vacuum micropumps to enable MEMS vacuum systems with both initial rough evacuation and long-term high vacuum maintenance capabilities.

Single-use MEMS sealing valve with integrated actuation for ultra low-leak vacuum applications

Human tissue engineering can save lives by providing donor tissues and organs, and by acting as a tool for screening new medical therapies before any human testing takes place. Tissue engineering has proven successful for certain types of tissue (e.g., skin [Wood et al. 07] and bladder [Atala et al. 06]) that have a more planar, sheet-like structure rather than a fully three-dimensional (3D) structure. The creation of more complex, fully 3D tissues has proven more challenging because of the need to create a functional (typically biomimetic) structure that is supported by appropriate vascular networks. Although some techniques have been demonstrated (e.g., bioprinting [Jakab et al. 10]), the current state of the art faces challenges in producing human tissue fast enough (i.e., with sufficient throughput), with complex human tissue structures suitable for transplantation or medical therapy testing (i.e., with sufficient control), and in a way that can be done to meet demand (i.e., with sufficient scalability). Origami offers potential to obtain well-controlled 3D structures for tissue engineering. Manual folding [Kuribayashi-Shigetomi and Takeuchi 11] and cell traction forces [Kuribayashi-Shigetomi et al. 12] have been used to fold nonbiodegradable parylene for tissue engineering. Nonbiodegradable polymeric microcontainers are folded to encapsulate biological specimens by a self-actuation process in [Azam et al. 11]. Patterned poly(ethylene glycol) (PEG) hydrogels are self-actuated and folded into structures with uniform radii of curvature for biological applications in [Jamal et al. 13]. In contrast to the previous demonstrations, the present work simulates and experimentally demonstrates actuated self-folding of biodegradable polymeric structures for tissue engineering in which well-defined hinges localize folding between the more rigid plates. The present concept for tissue engineering combines the previously demonstrated ability to organize cells of different sizes (e.g., of different cell types) into hemispherical wells on a two-dimensional (2D) sheet [Agarwal and Livermore 11] with origami folding. In this approach, spherical cells suspended in a liquid medium are assembled onto a polymer surface; the surface may be precoated with collagen to better promote the survival and correct function of the cells. Although cells can adhere anywhere on the surface, external

/pdf/toward-engineering-biological-tissues-by-directed-assembly-cvixbb3hlx.pdf

Carol Livermore

Papers

A Self-Excited MEMS Electro-Quasi-Static Induction Turbine Generator

Modeling and Characterizing Initial Component Assembly in Templated Assembly by Selective Removal

A compact architecture for passively-switched energy harvesters

Single-use MEMS sealing valve with integrated actuation for ultra low-leak vacuum applications

Toward engineering biological tissues by directed assembly and origami folding