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Piezoelectric actuators have been widely applied to precision positioning platforms. However, the positioning accuracy of piezoelectric ceramic has been significantly affected by its characteristics of hysteresis. Owing to the voltage-keeping feature of capacitive load for piezoelectric ceramic, this paper has proposed a switch-based driving in sequence method, which alternately drives each layer of PZT by using switches. Based on the driving in sequence method, the proposed method is capable of reducing the hysteresis to 1/N of the hysteresis under traditional voltage driving method, while significantly lowering the scale and cost of hardware, compared with the previous driving in sequence method. Thus, it allows for application to hundreds of layers of piezoelectric ceramic. According to experiment results, the hysteresis under different frequencies from 0.1 to 500 Hz for homemade seven-layer piezoelectric ceramic can be reduced from 12.5 to 2.1%. Furtherly, the residual hysteresis can be corrected by applying a simple quadratic-polynomial feedforward control, and the hysteresis is constrained within 0.8%, even with feedforward parameters that are not strictly calibrated. The dual-amplifier driving in sequence method proposed in this paper can significantly reduce the hysteresis in open-loop control of piezoelectric stack actuators, effectively improving the positioning and driving performance and saving cost. [ABSTRACT FROM AUTHOR]

Micro-electromechanical systems (MEMS)-based devices comprise suspended structures. A sacrificial layer is required to realize these structures. Usually, metal and dielectric materials are used as sacrificial layer materials. Metallic sacrificial material has a selectivity problem, whereas dielectric materials require higher deposition temperatures. Hence, in the present paper, photoresist (PR) material is used as the sacrificial layer. PR requires low-temperature processing and has no selectivity issues. Hence, photoresists are preferred as sacrificial layer materials. In the CMOS fabrication process, thin photoresists such as S1818, S1813, and AZ1505 are used. In these photoresists, the processing wafers are placed in a vertical position during patterning, which occupies less space. The recipes of such photoresists are well optimized for a uniform thickness across the wafer. However, special thick photoresists are used as a sacrificial layer for MEMS devices. These thick photoresists reflow in the vertical position and lead to non-uniform thickness; consequently, the yield is decreased. This paper has optimized a special thick photoresist (HiPR 6517) for RF MEMS SPST switches for better yield and uniformity. The measured pull-in voltage and the switch's resonant frequency are 13.00 V and 12.32 kHz, respectively. The fabricated switch offers isolation and insertion loss better than − 35 dB and − 1 dB at 24.5 GHz, respectively. [ABSTRACT FROM AUTHOR]

This paper presents a novel high multilevel inverter topology which is based on the created DC voltage levels at loads of the inverter. The circuit model is demonstrated by explaining the relationship between switches, sources and loads. According to the proposed inverter topology, the number of power switches connected to negative side of DC source is constant on inverter, while the number of power switches connected to positive side of DC sources is increasing. Therefore, linear pulse-width modulation (LPWM) is described for operating switches after pulse-width modulation method is developed to generate the PWM signals. Then, mathematical equations are given when resistive ( R), inductive ( L) and capacitive ( C) loads are connected in series on a 9-level inverter. Finally, the performances of the proposed inverters are observed through MATLAB/SIMULINK simulations after the designed multilevel inverters are simulated. So, 6-level, 9-level and 11-level inverters are compared with voltages, currents and harmonic distortions. Harmonic distortions reduce with increasing level of inverter, while three multilevel inverters are investigated on different modulation indexes. The results demonstrate the satisfactory performance of the inverter and verify the effectiveness of a novel high multilevel inverter topology. [ABSTRACT FROM AUTHOR]

Three- and four-port circulators based on resonators in 2D photonic crystals with square unit cell possessing a low symmetry are investigated. The three-ports are described by only one specific element named antiplane of symmetry. On the other hand, the four-port circulators formed by cascading these two three-ports can have one of the two symmetries. One of them is described by the antiplane of symmetry, and the other symmetry corresponds to a twofold rotational axis. The theoretical part of our paper concerns scattering matrix analysis of the devices with different symmetries and also the operation of the four-port circulator as a single-pole triple-throw switch. Finally, the calculated frequency responses of two circulators are presented. [ABSTRACT FROM AUTHOR]

Software features often span multiple directories and conceptual modules making the extraction of feature architectures difficult. In this work, we extract a feature toggle architectural view and show how features span the conceptual, concrete, and reference architectures. Feature toggles are simple conditional flags that allow developers to turn a feature on or off in a running system. They are commonly used by large web companies, including Google, Netflix and Facebook to selectively enable and disable features. Recently, libraries to help inject and manage toggles have been created for all the major programming languages. We extract the feature toggles from the Google Chrome web browser to illustrate their use in understanding the architecture of a system. Since there is no high-level conceptual and concrete architectures for Chrome, we had to manually derive these representations from available documentation and map them into the source code. These modular representations of a modern web browser allowed us to update the 12 year old research on browser reference architectures with current technologies and browser concepts. Mining the usages of feature toggles in the source code, we were able to map them on to the modular representation to create a feature toggle architectural view of Chrome. We are also able to show which features are contained in a module and which modules a feature spans. Throughout the paper, we show how the feature toggle view can give new perspectives into the feature architecture of a system. [ABSTRACT FROM AUTHOR]

new transmitter for ultra-wideband (UWB) impulse radio is described in this paper. The new UWB transmitter implements a low power Gaussian shaping filter to reduce the side-lobe in the frequency domain. A simple pulse amplitude modulation (PAM) circuit is used to keep the power consumption low. The proposed architecture features the simple design, low-power operation, and enables the pulse-shape generation for a multi-channel UWB. The core layout size is only 0.2 mm. The simulation results show that the generated signals satisfy the FCC spectrum mask, and the average power consumption is <1.97 mW for the 1.8 V supply voltage. Pulses are transmitted at a PRF (pulse repetition frequency) of 40.5 MHz in 500 MHz bandwidth channels equally spaced within the 3.1-10.6 GHz UWB. This transmitter is designed and fabricated in a 0.18-μm CMOS process. [ABSTRACT FROM AUTHOR]

system of Boolean equations is called sparse if each equation depends on a small number of variables. Finding efficiently solutions to the system is an underlying hard problem in the cryptanalysis of modern ciphers. In this paper we study new properties of the Agreeing Algorithm, which was earlier designed to solve such equations. Then we show that mathematical description of the Algorithm is translated straight into the language of electric wires and switches. Applications to the DES and the Triple DES are discussed. The new approach, at least theoretically, allows a faster key-rejecting in brute-force than with COPACOBANA. [ABSTRACT FROM AUTHOR]

In this review, we present one of the main areas of the work of the Laboratory of Physical Chemistry of Supramolecular Systems, Frumkin Institute of Physical Chemistry and Electrochemistry, Russian Academy of Sciences, devoted to studying monolayers and ultrathin films on liquid and solid surfaces. Numerous problems are discussed concerning the peculiarities of the supramolecular organization, behavior, and functional potential of these traditional colloidal systems. The article describes diverse examples of systems that form ultrathin organized films at different interfaces and the processes occurring in them, thereby reflecting the contemporary stage of the interconnection of related fields of science (colloid and supramolecular chemistry, nanotechnology, biomimetics, sensorics, etc.). Such a combination makes it possible to develop new intelligent nanostructured devices. Complexation in ultrathin layers of ligands on liquid and solid substrates is considered in connection with the use thereof as sensitive sensory elements in systems with reduced dimensionality. Substantial attention is focused on the aggregation behavior of diverse ligands and topochemical reactions in organized 2D ensembles, development of new methods for preparing two-dimensional organic networks, and creation of highly stable supramolecular devices based thereon. In the light of the features of 2D systems, several types of mechanochemical transformations occurring under the action of two-dimensional compression–expansion are considered: the phenomenon of redox isomerism in monolayers of lanthanide bis-phthalocyaninates, the phenomenon of forced axial coordination in tetrapyrrole complexes of nickel with a change in its spin number, and the phenomenon of the reversible formation of excimers. Especial attention is given to the problems concerning the behavior of organic photochromes at interfaces and the perspectives of developing molecular switches based on photosensitive compounds. [ABSTRACT FROM AUTHOR]

Modern era of wireless communication relies on the evolution of adaptive antennas. This influences the new age antenna designs to adapt themselves to the changing RF environment. Reconfigurable antennas are one such design where the operating frequency, radiation pattern, and polarization can be altered according to the user's requirement. Numerous research works have been contributed to the design of reconfigurable antennas. In view of that, this work proposes a detailed survey on reconfigurable antennas. The key motivation behind the survey is to provide an elaborate idea on the existing reconfigurable antenna designs so that the antenna researchers can perform possible analysis to overcome shortcomings or can enhance the performance of the existing designs. The evolution of reconfigurable antennas, the need for different reconfigurations and their design specifications are presented in this survey. Further, a comparative study on different switching mechanisms, deployment of various techniques to enhance antenna performance, diverse applications and existing design challenges are also addressed as a part of this review. Hence, this survey will be useful to the researchers in developing futuristic reconfigurable radiating structures that can be well suited for applications like Cognitive Radio, 5G and Multiple Input Multiple Output systems. [ABSTRACT FROM AUTHOR]

Bistable switch-like behavior is a ubiquitous feature of gene regulatory networks with decision-making capabilities. Type II toxin-antitoxin (TA) systems are hypothesized to facilitate a bistable switch in toxin concentration that influences the dormancy transition in persister cells. However, a series of recent retractions has raised fundamental questions concerning the exact mechanism of toxin propagation in persister cells and the relationship between type II TA systems and cellular dormancy. Through a careful modeling search, we identify how sp: bistablilty can emerge in type II TA systems by systematically modifying a basic model for the RelBE system with other common biological mechanisms. Our systematic search uncovers a new combination of mechanisms influencing bistability in type II TA systems and explores how toxin bistability emerges through synergistic interactions between paired type II TA systems. Our analysis also illustrates how Descartes' rule of signs and the resultant can be used as a powerful delineator of bistability in mathematical systems regardless of application. [ABSTRACT FROM AUTHOR]

We present an analysis of graphene-loaded transmission line switches for sub-millimeter wave and terahertz applications. As such, we propose equivalent circuit models for graphene-loaded coplanar waveguides and striplines and examine the switching performance under certain parameters. Specifically, we identify the optimum design of graphene switches based on transmission line characteristic impedance, scaling factor, graphene shape, and topology (series or shunt). These parameters are varied to obtain the insertion loss and ON/OFF ratio of each switch configuration. The extracted results act as the design roadmap toward an optimum switch topology and emphasize the limitations with respect to fabrication challenges, parasitic effects, and radiation losses that are especially pronounced in the millimeter wave/terahertz bands. This is the first time that such an in-depth analysis is carried out on graphene-loaded transmission line switches, enabling the development of efficient millimeter wave/terahertz tunable topologies in terms of insertion loss and ON/OFF ratio. Specifically, the optimized switches can be integrated with antennas or employed for the development of tunable phase shifters, leading to the implementation of efficient reconfigurable reflective surfaces (e.g., reflectarrays) or coded phased arrays either for imaging or wireless communication applications. In our models, we use measured graphene values (sheet impedance) instead of theoretical equations, to obtain the actual switching performance. Moreover, the proposed study can be easily expanded to other thin film materials that can be characterized by a sheet impedance including vanadium dioxide and molybdenum disulfide. Finally, the proposed equivalent models are crucial for this in-depth study; since we simulated more than 2,000,000 configurations, a computationally challenging task with the use of full-wave solvers. [ABSTRACT FROM AUTHOR]

High-speed and low-power reconfigurable photonic devices, such as thermally tunable devices, are needed for high throughput in optical communication networks. Based on thermo-electric coupling simulation and theoretical analysis, temperature response processes of the thermally tunable devices with suspended silicon waveguide proposed previously are investigated, with a focus on the effects of layer thicknesses and materials. The results show that the response time and the figure of merit (FOM) can both be reduced by 10% and 20% when the heater thickness varies from 0.16 to 0.08 μm and the cladding thickness decreases from 1.2 to 0.8 μm, respectively. The response time of devices with claddings of alumina, aluminum nitride and silicon nitride has an improvement of 50.8%, 59.8% and 83.5% separately compared with that of the device with silica cladding. Through these optimizations, it is demonstrated by the simulation that the response time and power consumption can be reduced to less than 20 μs and 1 mW separately for the thermally tunable switches. [ABSTRACT FROM AUTHOR]

An artificial molecular machine consists of molecule or substituent components jointed together in a specific way so that their mutual displacements could be initiated using appropriate outside stimuli. Such an ability of performing mechanical motions by consuming external energy has endowed these tiny machines with vast fascinating potential applications in areas such as actuators, manipulating atoms/molecules, drug delivery, molecular electronic devices, etc. To date, although vast kinds of molecular machine archetypes have been synthesized in facile ways, they are inclined to be defined as switches but not true machines in most cases because no useful work has been done during a working cycle. More efforts need to be devoted on the utilization and amplification of the nanoscale mechanical motions among synthetic molecular machines to accomplish useful tasks. Here we highlight some of the recent advances relating to molecular machines that can perform work on different length scales, ranging from microscopic levels to macroscopic ones. [ABSTRACT FROM AUTHOR]

We consider the problem of managing a bounded size First-In-First-Out (FIFO) queue buffer, where each incoming unit-sized packet requires several rounds of processing before it can be transmitted out. Our objective is to maximize the total number of successfully transmitted packets. We consider both push-out (when a policy is permitted to drop already admitted packets) and non-push-out cases. We provide worst-case guarantees for the throughput performance of our algorithms, proving both lower and upper bounds on their competitive ratio against the optimal algorithm, and conduct a comprehensive simulation study that experimentally validates predicted theoretical behavior. [ABSTRACT FROM AUTHOR]

We developed new optical switches based on nematic and ferroelectric liquid crystal (LC) cells for photonics applications. Certain new LC switches based on the effect of total internal reflection in nematic LC and deformed helix ferroelectric effect ferroelectric LC with very fast response time were developed. Fast bistable optical switches of the light polarization based on ferroelectric liquid crystal cells were proposed. The switches are characterized by 100 ìs switching time and 26 dB crosstalk at the wavelength of 632.8 nm and bistable, i.e., required zero power consumption in the switch state. High frequency hysteretic free electrically controlled 0–2π phase modulation of light has been proposed using a very short helix pitch (less than 400 nm) deformed helix ferroelectric liquid crystal. The electrically controlled 0–2π hysteretic free phase modulation was achieved at the driving voltage frequency up to 4 kHz and the voltage amplitude of 32 V. The application of fast V-shaped deformed helix ferroelectric ferroelectric LC (DHF-FLC) for new active-matrix liquid crystal display (LCD) and optical data processing devices is envisaged. Photoalignment technology can be very useful for the new generation of liquid crystal devices as well as in new photovoltaic, optoelectronic and photonic devices based on highly ordered thin organic layers. We have investigated the LC photoalignment in superthin tubes, which are basic elements of switchable photonic crystal/liquid crystal structures and obtained the order parameter comparable with usual homogeneous nematic LC cells. We studied LC alignment on silicon surfaces with submicrometer-sized straight and curved waveguide profiles. The liquid crystal cladding refractive index was then varied according to the applied voltage, and subsequently the microresonator resonance wavelengths were tuned. Based on our initial measurements, the free spectral range (FSR) wavelength shift within the range of 20 nm was obtained, which is comparable with a thermooptic effect. The new voltage controllable Si-based add drop filters are envisaged based on this principle. [ABSTRACT FROM AUTHOR]

We formulate a model for the optimal location of switches in ATM communications networks. The networks are designed in such a way that, at their arrival to the switches, ATM cells find free space in a buffer of length b, with a probability α. The model avoids the impairment to the communication caused by both cell loss (because of shorter buffers) and cell-delay variations (because of longer buffers). It is also shown how to transform a non-linear, probabilistic, constraint into a linear form. Computational experience is provided for the model. [ABSTRACT FROM AUTHOR]