Class Of Switches Research Articles

How to Switch Spin-Crossover Metal Complexes at Constant Room Temperature.

Spin-crossover metal complexes represent a highly promising class of molecular switches, the diverse physicochemical properties of which can be reversibly changed by different physical and chemical stimuli. One of the most interesting and examined features of these materials is the change of magnetic properties by changing the temperature or by irradiation with light at low temperatures. However, most prospective applications of such complexes require functioning at room temperature. This Concept article provides an overview about how the switching of spin-crossover metal complexes can be achieved at constant room temperature. The principles of switching by different physical and chemical methods in solution and in the solid state are presented in an easy-to-read form for nonspecialists. These are further supported and clarified by examples from the literature. The overview might also be interesting for experts that target spin-crossover systems functioning at ambient conditions.

New Class of Rearrangeable Nonblocking Multicast Free-Space Optical Switches

In this paper, we propose N × N rearrangeable nonblocking multicast free-space optical switches. Our design exploits nonmovable tri-state switching elements (T-SEs) that support signal splitting and switching simultaneously and seamlessly, and thus, separate splitting stages used in the conventional multicast switches are not needed. It follows that the propagation loss that may be encountered by an optical beam passing through a splitting stage followed by a crossbar (e.g., splitter-and-delivery-based switches) can be avoided in the proposed switch, since the beam passes through only a single stage. The proposed switch exhibits an optimal hardware complexity, as it requires only N(N + 1) /2 T-SEs. The switch is analyzed and compared to existing optical multicast switches in terms of hardware complexity, power loss, and cost. Comparison results show that the proposed switch provides multicast capability with a lower hardware complexity and a comparable performance. Cost analysis shows that for N = 4, the overall cost of the new design is lower than that of existing strictly nonblocking switches, even if the T-SE is 3.5 to 10 times the cost of typical microelectromechanical systems mirrors. In addition, we present a simple routing algorithm that systematically establishes connections over the new switch.

Design of a High Linearity 6-GHz Class-F Radio Frequency Power Amplifier

In this study, a high linearity class-F RF power amplifier is introduced. It is designed to operate at a frequency of 6 GHz with a bandwidth of 400MHz. The amplifier mixes between the characteristics of conventional switch mode class-F and class B amplifiers. It is biased at very low quiescent power, thus it dissipates negligible DC power in the absence of RF excitation. This makes it suitable for handset applications. The amplifier is designed and tested on Microwave Office Environments. It showed linear input/output characteristics for an input RF power range of -20 to 5d Bm. The amplifier collector efficiency is 80%, which is greater than that of ideal class-B power amplifier. In addition, it is sensitive to amplify low level RF signals, therefore it needs no preamplifier.

Switching Signal Estimator Design for a Class of Elementary Systems

The goal of this technical note is to design a switching signal estimator for a class of elementary continuous-time switching or switched systems. First, the elementary system is recast into a polynomial form and, secondly, some tools borrowed from Algebraic Geometry are used to express the switching signal as a function of the time derivatives of the output and of the input.

Oxazines: A New Class of Second-Order Nonlinear Optical Switches.

A combined experimental-theoretical investigation has revealed that oxazine-based compounds are multiaddressable, multistate, and multifunctional molecular switches exhibiting contrasts of both linear and second-order nonlinear optical properties. The switching properties are particularly large when the substituent is a donor group. In this study, the cleavage of the C-O bond at the junction of the indole and oxazine cycles (of the closed a forms) is acido-triggered, leading to an open form (b(+)) characterized by larger first hyperpolarizabilities (βHRS) and smaller excitation energies than in the closed form. These results are confirmed and interpreted utilizing ab initio calculations that have been carried out on a broad set of compounds to unravel the role of the substituent. With respect to acceptor groups, oxazines bearing donor groups are characterized not only by larger βHRS and βHRS contrast ratios but also by smaller excitation energies, larger opening-induced charge transfer, and reduction of the bond length alternation, as well as smaller Gibbs energies of the opening reaction. Compared to protonated open forms (b(+)), calculations on the zwitterionic open forms (b) have pointed out similarities in the long-wavelength UV/vis absorption spectra, whereas their βHRS values might differ strongly as a function of the substituent. Indeed, the open forms present two NLOphores, the indoleninium-substituent entity and the nitrophenol (present in the protonated open form, b(+)) or nitrophenolate (present in the zwitterionic open form, b) moiety. Then, nitrophenolate displays a larger first hyperpolarizability than nitrophenol and the β tensor of the two entities might reinforce or cancel each other.

Sigma Delta Modulator Based Multi-Standard Transmitter Design For Wireless Communication Applications

This paper presents a sigma delta modulator (ƩΔM) based transmitter that is suitable for digital multi-standard wireless applications especially for software defined radio (SDR) systems. The proposed transmitter mainly consists of a sigma-delta modulator and a switching-mode power amplifier. In the proposed design, a third order low-pass ƩΔM is implemented to produce a high frequency digital-like signals that is used to drive a high efficient class-E switching mode power amplifier. The target technology for fabrication is TSMC180nm CMOS process. The proposed design is tested for different standards such as Global System for Mobile Communications (GSM), Universal Mobile Telecommunications System (UMTS), Wi-Fi and Long Term Evolution (LTE) with frequency bands of (1.8GHz, 2.1GHz, 2.4GHz, (1.9, 2.6GHz)) respectively. The class-E power amplifier has shown peak power added efficiency (PAE) and peak output power of 62/58.7/60/52/47% and 27.7/27.5/27.6/27/26.7dBm, respectively, at the mentioned standards. Moreover, the proposed power amplifier can cover a wide range of frequency from 1.8GHz to 2.6GHz maintaining high efficiency.

On a Class of Hybrid Differential Games

This paper is intended to present a systematic application of the hybrid systems framework to differential games. A special class of bimodal linear-quadratic differential games is presented and illustrated with examples; two particular classes of switching rules, time-dependent and state-dependent switches are discussed. The main contribution of the paper consists in formulating necessary optimality conditions for determining optimal strategies in both cooperative and non-cooperative cases. A practically relevant hybrid differential game of pollution reduction is considered to illustrate the developed framework.

Performance evaluation of hybrid optical switch architecture for data center networks

In response to the need for high bandwidth and power efficient data center interconnection networks, different interconnects have been proposed based on the optical technology used: micro-electromechanical system (MEMS), optical cross connects (OXCs), arrayed waveguide grating routers (AWGRs) and semiconductor optical amplifier (SOAs). MEMS switches are based on mature technology, have low insertion loss and cross-talk, and are data rate independent. They are also the most scalable and the cheapest class of optical switches. However, the reconfiguration time of these switches is of the order of tens of milliseconds while fast optical switches have switching time in the range of a few nanoseconds. Fast optical switches can be based on AWGRs in conjunction with tunable wavelength converters or tunable lasers or they are based on SOAs in broadcast-and-select architecture. In this paper, we propose an optical interconnect architecture for the large scale data centers. The proposed interconnect: Hybrid Optical Switch Architecture (HOSA) is a hybrid design that features slow and fast optical switches. The hybrid design leverages strengths of both types of optical switches. To reduce complexity, we employ a single stage core topology that can be easily scaled up (in capacity) and scaled out (in the number of racks) without requiring major re-cabling and network reconfiguration. We investigate the scalability of the HOSA and show that by using a single stage core topology, it can be scaled to a hundreds of thousands of servers. We also investigate a trade-off between cost and power consumption of our design by comparing it with other well-known interconnects by using analytical modelling. We demonstrate power efficiency as compared to other conventional interconnects on account of upfront CAPEX but the additional CAPEX incurred in deploying our solution instead of traditional architecture is mitigated to some extent by reduced OPEX, due to its greater energy efficiency. We evaluate the performance of the system using network-level simulation by considering diverse workload communication patterns and system design parameters. Our results show low latency and high throughput with different workload communication patterns.

Understanding conductivity in molecular switches: a real space approach in octaphyrins.

In recent years, expanded porphyrins have emerged as a promising class of π-conjugated molecules that display unique electronic, optical and conformational properties. Several expanded porphyrins can switch between planar and twisted conformations, which have different photophysical properties. Such a change of topology involves a Hückel-Möbius aromaticity switch in a single molecule and it can be induced by solvent, pH and metallation. These features make expanded porphyrins suitable for the development of a novel type of molecular switches for molecular electronic devices. Octaphyrins consisting of eight pyrrole rings, exhibit twisted-Hückel, Möbius and Hückel π-conjugation topologies depending on the oxidation and protonation state, with distinct electronic structures and aromaticity. Our working hypothesis is that a significant change in the conductance of expanded porphyrins will be observed after the topology switching. Despite the potential of Hückel-Möbius systems as conductance switches, the relationship between the conductance and the molecular topology is not yet understood. We have explored the performance of local descriptors of conductivity in simple molecules, as well as the relationship with conductance. Since these indexes provide a qualitative measure of delocalization and conductance in the probe molecules, we have carried out a local analysis of electrical conductance changes as a function of the π-conjugation in two examples. In one of them, the locality of the electronic changes ensures the ability of these indexes to describe the conductance as local. Moreover, it enables to identify which conformational switch would be more efficient from an electronic device perspective. However, we also show that it is not always possible to reduce conductance changes to one bond, and in those molecules where a deep rearrangement occurs far from the structural perturbation, local measures show a limited efficiency. This is a first step for the description of the connection between the molecular structure and conductance in molecular switches.

Harnessing Deformation to Switch On and Off the Propagation of Sound.

A new class of architected materials is designed to control the propagation of sound. The proposed system comprises an array of elastomeric helices in background air and is characterized by frequency ranges of strong wave attenuation (bandgaps) in the undeformed configuration. Upon axially stretching the helices, such bandgaps are suppressed, enabling the design of a new class of acoustic switch.

Analysis and Design of Loosely Inductive Coupled Wireless Power Transfer System Based on Class-<formula formulatype="inline"><tex Notation="TeX">${\rm E}^{2}$</tex></formula> DC-DC Converter for Efficiency Enhancement

This paper presents a design procedure of high-frequency loosely inductive coupled wireless power transfer (LIC-WPT) system based on class- ${\rm E}^{2}$ dc-dc converter, taking into account the power loss reduction of inverter, coupling part, and rectifier simultaneously. Analytical expressions including the dc-to-dc efficiency of the WPT system are derived and the efficiency deterioration mechanism is explained by the circuit model. Through the analytical expressions, the design procedure for satisfying both the class-E switching conditions and power loss reductions at the coupling part is proposed from the circuit-theory viewpoint. The class- ${\rm E}^{2}$ WPT system designed by the proposed design procedure achieves high dc-to-dc efficiency at low coupling coefficient, in particular, compared with those designed by the previous design strategies. The validity and effectiveness of the proposed design procedure were confirmed by PSpice simulations and circuit experiments.

A 240 GHz Fully Integrated Wideband QPSK Transmitter in 65 nm CMOS

In this paper, a 240 GHz 16 Gbps QPSK transmitter is demonstrated in 65 nm bulk CMOS process. The transmitter chain employs an 80 GHz local oscillator and a modulator to generate the data that is amplified by a class-E switching power amplifier. The amplified signal then drives the 240 GHz tripler to generate the required modulated data. By using on-chip slotted loop antennas, the transmitter achieves an EIRP of 1 dBm. A maximum data rate of 16 Gbps is achieved with a transmitter efficiency of 14 pJ/bit.

Conformational flexibility of viral RNA switches studied by FRET

The function of RNA switches involved in the regulation of transcription and translation relies on their ability to adopt different, structurally well-defined states. A new class of ligand-responsive RNA switches, which we recently discovered in positive strand RNA viruses, are distinct from conventional riboswitches. The viral switches undergo large conformational changes in response to ligand binding while retaining the same secondary structure in their free and ligand-bound forms. Here, we describe FRET experiments to study folding and ligand binding of the viral RNA switches. In addition to reviewing previous approaches involving RNA model constructs which were directly conjugated with fluorescent dyes, we outline the design and application of new modular constructs for FRET experiments, in which dye labeling is achieved by hybridization of a core RNA switch module with universal DNA fluorescent probes. As an example, folding and ligand binding of the RNA switch from the internal ribosome entry site of hepatitis C virus is studied comparatively with conventional and modular FRET constructs.

Ligand-responsive RNA mechanical switches

Ligand-responsive RNA mechanical switches represent a new class of simple switching modules that adopt well-defined ligand-free and bound conformational states, distinguishing them from metabolite-sensing riboswitches. Initially discovered in the internal ribosome entry site (IRES) of hepatitis C virus (HCV), these RNA switch motifs were found in the genome of diverse other viruses. Although large variations are seen in sequence and local secondary structure of the switches, their function in viral translation initiation that requires selective ligand recognition is conserved. We recently determined the crystal structure of an RNA switch from Seneca Valley virus (SVV) which is able to functionally replace the switch of HCV. The switches from both viruses recognize identical cognate ligands despite their sequence dissimilarity. Here, we describe the discovery of 7 new switches in addition to the previously established 5 examples. We highlight structural and functional features unique to this class of ligand-responsive RNA mechanical switches and discuss implications for therapeutic development and the construction of RNA nanostructures.

Contacts for organic switches with carbon-nanotube leads

We focus on two classes of organic switches operating due to the photo- or field-induced proton transfer (PT) process. By means of first-principles simulations, we search for the atomic contacts that strengthen diversity of the two swapped current–voltage (I–V) characteristics between two tautomers. We emphasize that the low-resistive contacts do not necessarily possess good switching properties. Very often, the higher-current flow makes it more difficult to distinguish between the logic states. Instead, the more resistive contacts multiply a current gear to a larger extent. The low- and high-bias work regimes set additional conditions, which are fulfilled by different contacts: (i) in the very low-voltage regime, the direct connections to the nanotubes perform better than the popular sulfur contacts, and (ii) in the higher-voltage regime, the best are the peroxide (-O-O-) contacts. Additionally, we find that the switching-bias value is not an inherent property of the conducting molecule, but it strongly depends on the chosen contacts.

Graphs with many valencies and few eigenvalues

Dom de Caen posed the question whether connected graphs with three distinct eigenvalues have at most three distinct valencies. We do not answer this question, but instead construct connected graphs with four and five distinct eigenvalues and arbitrarily many distinct valencies. The graphs with four distinct eigenvalues come from regular two-graphs. As a side result, we characterize the disconnected graphs and the graphs with three distinct eigenvalues in the switching class of a regular two-graph.

An adaptive digital processor for power efficiency enhancement in hybrid supply modulators

SummaryA novel digital envelope modulator for envelope tracking radio frequency power amplifier is presented in this paper. The proposed modulator consists of a parallel combination of linear class AB and switching class D power amplifiers that are controlled digitally. In the previous analog architectures, the requirements needed for the AB operational amplifier such as high‐current driving capability, high bandwidth and large output swing is usually obtainable at high overall static power dissipation. The digitally controlled power opamp presented here not only provides the aforementioned requirements but also reduces power dissipation compared with previous work. Furthermore, the digital control of the modulator makes it adaptive to the input signal variations in comparison with conventional analog parallel hybrid envelope modulators. The digital processor of the modulator is evaluated with a 45‐nm complementary metal oxide semiconductor technology. The overall power consumption of the digital processor is around 142 mW at 1.5‐GHz clock frequency. As an application, the designed digital class AB is incorporated in a complete envelope modulator architecture. The overall efficiency of the modulator, including the digital processor power consumption, is around 82% at an average 32 dBm output power for a 5‐MHz input signal. Copyright © 2015 John Wiley & Sons, Ltd.

On graphs with maximum size in their switching classes

In his PhD thesis [Structural aspects of switching classes, Leiden Institute of Advanced Computer Science, 2001] Hage posed the following problem: “characterize the maximum size graphs in switching classes”. These are called s-maximal graphs. In this paper, we study the properties of such graphs. In particular, we show that any graph with sufficiently large minimum degree is s-maximal, we prove that join of two s-maximal graphs is also an s-maximal graph, we give complete characterization of triangle-free s-maximal graphs and non-hamiltonian s-maximal graphs. We also obtain other interesting properties of s-maximal graphs.

Stabilization of a Class of Switched Positive Nonlinear Systems

The problem of switching stabilization for a class of switched positive nonlinear systems (switched positive homogeneous cooperative system (SPHCS) in the continuous-time context and switched positive homogeneous order-preserving system (SPHOS) in the discrete-time context) is studied by using average dwell time (ADT) approach, where the positive subsystems are possibly all unstable. To tackle this problem, a new class of ADT switching is first defined, which is different from the previous defined ADT switching in the literature. Then, the proposed ADT is designed via analyzing the weightedl∞norm of the considered system’s state. A sufficient condition of stabilization for SPHCSs with unstable positive subsystems is derived in continuous-time context. Furthermore, a sufficient condition for SPHOSs under the assumption that all modes are possibly unstable is also obtained. Finally, a numerical example is given to demonstrate the advantages and effectiveness of our developed results.

Lyapunov‐based robust control design for a class of switching non‐linear systems subject to input saturation: application to engine control

Control technique based on the well-known Takagi–Sugeno (T–S) models offers a powerful and systematic tool to cope with complex non-linear systems. This study presents a new method to design robust H ∞ controllers stabilising the switching uncertain and disturbed T–S systems subject to control input saturation. To this end, the input saturation is taken into account in the control design under its polytopic form. The Lyapunov stability theory is used to derive the design conditions, which are formulated as a linear matrix inequality (LMI) optimisation problem. The controller design amounts to solving a set of LMI conditions with some numerical tools. In comparison with previous results, the proposed method not only provides a simple and efficient design procedure to deal with a large class of input saturated non-linear systems but also leads to less conservative design conditions. Moreover, with a simple shape criterion, the proposed approach maximises also the estimated domain of attraction included inside the validity domain of the system. The validity of the proposed method is illustrated through academic as well as real industrial examples.