Passive Switching Research Articles

Combined dual-channel fluorescence depth sensing of indocyanine green and protoporphyrin IX kinetics in subcutaneous murine tumors.

Fluorescence sensing within tissue is an effective tool for tissue characterization; however, the modality and geometry of the image acquisition can alter the observed signal. We introduce a novel optical fiber-based system capable of measuring two fluorescent contrast agents through 2cm of tissue with simple passive electronic switching between the excitation light, simultaneously acquiring fluorescence and excitation data. The goal was to quantify indocyanine green (ICG) and protoporphyrin IX (PpIX) within tissue, and the sampling method was compared with wide-field surface imaging to contrast the value of deep sensing versus surface imaging. This was achieved by choosing filters for specific wavelengths that were mutually exclusive between ICG and PpIX and coupling these filters to two separate detectors, which allows for direct swapping of the excitation and emission channels by switching the on-time of each excitation laser between 780- and 633-nm wavelengths. This system was compared with two non-contact surface imaging systems for both ICG and PpIX, which revealed that the fluorescence depth sensing system was superior in its ability to resolve kinetics differences in deeper tissues that would normally be dominated by strong signals from skin and other surface tissues. Specifically, the system was tested using pancreatic adenocarcinoma tumors injected into murine models, which were imaged at several time points throughout tumor growth to its diameter. This demonstrated the system's capability to track longitudinal changes in ICG and PpIX kinetics that result from tumor growth and development, with larger tumors showing sluggish uptake and clearance of ICG, which was not observable with surface imaging. Similarly, PpIX was quantified, which showed slower kinetics over different time points, and was further compared with the wide-filed imager. These results were further validated through depth measurements in tissue phantoms and model-based interpretation. This fluorescence depth sensing system can be used to sample the interior blood flow characteristics by ICG sensing of tissue as deep as 20mm into the tissue with sensitivity to kinetics that are superior to surface imaging and may be combined with other imaging modalities such as ultrasound to provide guided deep fluorescence measurements.

Seamless switching, feedforward, and feedback mechanisms: Enhancing task performance and user perception in device switch

In an era where digital multitasking is universal, the necessity to switch between devices is vital. The effect of switching modes between devices on the user experience remains unclear. This study investigates the impact of switching modes on task performance and user perception within interconnected device environments. A within-subject experiment utilizing memory recall tasks was implemented to test three switching modes: seamless switching, passive switching, and switching with feedforward and feedback. Task accuracy rate, perceived interruption, perceived control, and behavioral intention were measured. Results indicated that seamless switching outperformed passive switching in task accuracy rate. Passive switching elicited the highest level of perceived interruption, while switching with feedforward and feedback substantially improved the perceived control of users over seamless switching. The behavioral intention to use seamless switching and switching with feedforward and feedback was considerably higher than that for passive switching. This research provides insights into the comparative benefits of seamless switching and switching with feedforward and feedback, particularly regarding their influence on user perception. Practical implications for the design of interconnected device switching and the management of device ecosystems are also presented.

An emergent attractor network in a passive resistive switching circuit

Resistive memory devices feature drastic conductance change and fast switching dynamics. Particularly, nonvolatile bipolar switching events (set and reset) can be regarded as a unique nonlinear activation function characteristic of a hysteretic loop. Upon simultaneous activation of multiple rows in a crosspoint array, state change of one device may contribute to the conditional switching of others, suggesting an interactive network existing in the circuit. Here, we prove that a passive resistive switching circuit is essentially an attractor network, where the binary memory devices are artificial neurons while the pairwise voltage differences define an anti-symmetric weight matrix. An energy function is successfully constructed for this network, showing that every switching in the circuit would decrease the energy. Due to the nonvolatile hysteretic function, the energy change for bit flip in this network is thresholded, which is different from the classic Hopfield network. It allows more stable states stored in the circuit, thus representing a highly compact and efficient solution for associative memory. Network dynamics (towards stable states) and their modulations by external voltages have been demonstrated in experiment by 3-neuron and 4-neuron circuits.

An integrated common ground‐based grid‐connected current‐fed switched inverter

AbstractA current‐fed switched inverter and its derivatives are gaining more attention in solar PV grid‐connected applications. In these inverters, the absence of galvanic isolation generates the leakage current, leading to the injection of harmonics and the degradation of solar PV panel life span. This paper proposes an integrated common ground‐based grid‐connected current‐fed switched inverter. The common ground between the input DC source and output AC grid eliminates the leakage current and makes the inverter immune to high‐frequency common‐mode voltage variations. It utilizes the shoot‐through state to boost the input DC voltage and obtain the rated AC output voltage. Moreover, as compared to the contemporary common ground‐based inverter topologies, the number of passive reactive elements and active switches is less. Thereby, the size, cost of the system, and associated power loss are reduced. The proposed inverter's continuous input current and buck–boost nature make it suitable for applications like solar PV systems. The steady‐state analysis of the proposed inverter is validated using the MATLAB Simulink tool, and furthermore, the simulation results during grid‐tied mode have been cross‐verified with the help of real‐time simulator OPAL‐RT. Further, the power loss and thermal loss analysis are carried out using the PLECS software. Finally, the performance of the inverter and simulation results are verified with the experimental results.

Reducing Automotive Cooling System Complexity through an Adaptive Biomimetic Air Control Valve.

Future automotive mobility is predominantly electric. Compared to existing systems, the requirements of subsystems change. Air flow for cooling components is needed predominantly when the car is in rest (i.e., charging) or at slow speeds. So far, actively driven fans consuming power and generating noise are used in this case. Here we propose a passive adaptive system allowing for convection-driven cooling. The developed system is a highly adaptive flat valve derived from the bordered pit. It was developed through an iterative design process including simulations, both structural and thermodynamic. In hardwoods and conifers, bordered pits enable the challenging transport of vertical fluids by locally limiting damage. Depending on the structure, these can close at sudden pressure changes and take the function of valves. The result of the biomimetic abstraction process is a system-integrative, low-profile valve that is cheap to produce, long-lasting, lightweight, maintenance-free, and noise-free. It allows for the passive switching of air flow generation at the heat exchanger of the cooling between natural convection or an active airstream without the need for complex sensing and control systems. The geometric and material design factors allow for the simple tuning of the valve to the desired switching conditions during the design process.

A novel thermal bus architecture for large cryogenic space telescopes utilizing helium pulsating heat pipes

Future space telescopes, such as those proposed for the Far-infrared Surveyor Mission, are expected to employ actively cooled optical arrays with a similar overall surface area compared to the James Webb Space Telescope. Therefore, there is a need for a cryogenic cooling system with a thermal bus architecture that can distribute cooling to these large optical arrays. Recent experimental research of helium Pulsating Heat Pipes (PHPs) has shown that helium PHPs can transfer heat over long distances (on the order of 2 m) with high efficiency, and also have the ability to act as a passive thermal switch upon the removal of the cooling source. PHPs’ high thermal performance, passive switching capability, low mass, and ease of manufacturing make them an appealing option compared to high-purity metal straps for a thermal bus architecture on large cryogenic space telescopes. A novel architecture for the thermal control of optical arrays is proposed utilizing unique configurations of helium pulsating heat pipes that minimize mass, maximize thermal performance, and reduce the risk of mission failure.

A 55 μ W 2.4 GHz wake-up receiver with offset-based peak detection achieving −90dBm sensitivity for IoT applications

The paper proposes a 2.4 GHz ultra-low power wake-up receiver (WuRX) with offset-based peak detection and mixer-first based radio frequency (RF) front-end for IoT applications. The mixer-first based front-end eliminates RF modules to reduce power consumption. Based on the transparency of the passive mixing switches, a 2-path passive mixer (2-PPM) constructs the high-Q band-pass filter (BPF) at the RF port to improve out-of-band blocker rejection. The offset-based peak detection circuit adaptively extracts the reference voltage for the subsequent comparator according to the real-time signal amplitude of envelope detection, which eliminates the misjudgment of the comparator and improves the accuracy of demodulation. For low power consumption, a ring oscillator is used to generate the local oscillator (LO) signal and the frequency calibration scheme combined with coarse tuning and fine tuning is employed to improve the frequency stability, which completes 10-bit frequency tuning with 2 MHz resolution. Designed in TSMC 28 nm CMOS technology, the mixer-first based front-end achieves a conversion gain of 42 dB and a noise figure of 11.9 dB at 2.4 GHz, an S11 less than −15dB during 2.4–2.5 GHz. The frequency calibration scheme for the ring oscillator completes the 512 MHz dynamic range with a 2 MHz frequency tuning step. The WuRX can achieve −90dBm sensitivity with 55 μ W power consumption at 0.6 V supply voltage and the chip area of 0.19 mm × 0.24 mm.

A capacitor-free driving stage for light emitting diodes

Electrolytic capacitors have the disadvantage of pronounced aging. Non-electrolytic capacitors are therefore used in applications where long-life is important. In this paper we present a driving stage for LEDs without any capacitive elements. The basic topology is a Buck converter with one coil, one active, and one passive switch. Instead of the output capacitor, series connections of one or more LEDs and an active switch are connected. An additional diode is connected between the output and the input to achieve a current path, when all LED-paths are off. A nonlinear hysteresis controller is used to achieve a robust control. A system with three switchable LED-strings is analyzed. Design hints are given and the function is proved with the help of LTSpice simulations. The system can be used for lighting purposes with the possibility to change the chrominance. The potentiality to transmit data is also treated.

Multi-Wavelength Selective and Broadband Near-Infrared Plasmonic Switches in Anisotropic Plasmonic Metasurfaces.

Anisotropic plasmonic metasurfaces have attracted broad research interest since they possess novel optical properties superior to natural materials and their tremendous design flexibility. However, the realization of multi-wavelength selective plasmonic metasurfaces that have emerged as promising candidates to uncover multichannel optical devices remains a challenge associated with weak modulation depths and narrow operation bandwidth. Herein, we propose and numerically demonstrate near-infrared multi-wavelength selective passive plasmonic switching (PPS) that encompasses high ON/OFF ratios and strong modulation depths via multiple Fano resonances (FRs) in anisotropic plasmonic metasurfaces. Specifically, the double FRs can be fulfilled and dedicated to establishing tailorable near-infrared dual-wavelength PPS. The multiple FRs mediated by in-plane mirror asymmetries cause the emergence of triple-wavelength PPS, whereas the multiple FRs governed by in-plane rotational asymmetries avail the implementation of the quasi-bound states in the continuum-endowed multi-wavelength PPS with the ability to unfold a tunable broad bandwidth. In addition, the strong polarization effects with in-plane anisotropic properties further validate the existence of the polarization-resolved multi-wavelength PPS. Our results provide an alternative approach to foster the achievement of multifunctional meta-devices in optical communication and information processing.

Re-routable and Low-latency All Optical Switching Algorithm for Next Generation DCN

Digital infrastructure is now indispensable to the function of society and quality of life of the citizen. All over the world there is leveraging of digital infrastructure that comprises use of data, computerized devices, methods and systems. During COVID-19 pandemic it comes more prominently in front. India being the most popular and populated country in the world, comprises nearly half billion internet users expected to transform the digital ecosystem. With the increasing demand of smartphone application, online activities gigantic amount of data has been generated, so evolution and development of data centers be the high importance not only for India but as well as for the world. Thus, it is the need to promote and create robust data center network infrastructure that supports emerging technologies such as 5G, IoT, AI, machine learning, adaptive manufacturing, smart agriculture, and automation and so on. In this paper we propose an all Optical re-routable, low latency Data Center Network (DCN) architecture using Passive Optical Datacenter Switch (PODS). The PODS consists of an Arrayed Waveguide Grating Router (AWGR) in association with a controller unit. An efficient wavelength assignment algorithm is integrated in PODS, to reroute the packet for congestion avoidance and packet loss.. This feature makes the DCN architecture more scalable, proficient with high throughput, low latency, power efficient under high traffic and bursty traffic conditions. The performance of the proposed PODS-based DCN is compared with existing passive optical DCN architectures PODCA and finds improved characteristics in terms of delay, throughput and blocking probability. Simulation of the framework is done in Python platform and executed on google COLAB in the Windows environment and the result shows 46.3% improvement in latency and throughput in terms of 90% network load compared with PODCA architecture.

Dispersion-flattened femtosecond mid-IR Cr:ZnS laser with a passive optical switch based on graphene–ZnSe

Dispersion-flattened femtosecond mid-IR Cr:ZnS laser with a passive optical switch based on graphene–ZnSe

Self-switching circuit of TENG for energy storage and power management in harvesting wind energy

As an important green energy in our life, natural wind energy is widely used in power generation. Triboelectric nanogenerator (TENG) can convert wind energy in the environment into electrical signal. In this study, two independent TENGs in parallel (FHS-TENG) and the power management circuit composed of passive self-switching circuit and LC filter circuit constitute a self-supplying system, which is committed to harvesting wind energy in the environment and outputting stable voltage and improving energy storage performance. The self-switching circuit mainly includes rectifier module, energy storage module, the self-switching module, and filter module. And the on/off state of the passive self-switching is mainly controlled by two transistors, which implements the effect of switch. The results demonstrate that the energy stored by the power management circuit is more than 100 times higher than that of the universal circuit at 100 μF capacitor, and the calculator is in stable working order in simulated wind conditions. This work provides a new strategy for the passive electronic switch of TENG and the improvement of circuit energy storage performance, which is meaningful for the further application and industrialization of TENG.

Switching on Versatility: Recent Advances in Switchable Plasmonic Nanostructures

Plasmonic nanostructures are emerging as a promising avenue for nanophotonics due to their extreme light and thermal confinement, ultrafast manipulation processes, and potential uses in device miniaturization. However, their fixed functions have limited their versatility in applications. This review provides an overview of recent switchable plasmonic nanostructure engineering techniques, focusing on methods that provide reversible switchability. Passive optical switching, active structure‐tunable switching, active material‐based switching, and advanced applications, such as multifunctional biomedical sensing, energy harvesting, and dynamic optical devices, are discussed. The specific methods and techniques used to engineer switchable plasmonic nanostructures are also highlighted. By understanding the latest developments and overall trends, this review is expected to help researchers design and fabricate advanced plasmonic nanostructures with unprecedented switchability and versatility for various applications.

An Asymmetrical Dual Quasi-Z-Source Based 7-Level Inverter for PV Applications

This paper presents a new single-stage quasi-z-source (qZS) based power converter for Photovoltaic (PV) applications. This seamless topology is obtained by the fusion of two quasi-z-source networks with a 7-level cascaded multilevel inverter (MLI). The proposed converter requires fewer passive components and power switching devices compared to the seven-level topologies with impedance and quasi-impedance sources, reported in the literature. The proposed modulation technique achieves the required level of voltage boosting using the qZS networks while synthesizing seven levels in the output voltage waveform. While the proposed power converter can regulate the output voltage in the standalone mode, it can inject active power into the grid at Unity power factor (UPF) in the grid-connected mode of operation. This paper also aims to mitigate the leakage current, which is one of the major issues in transformerless PV inverters, by reducing the magnitude of voltage transitions in the parasitic capacitor and the suppression of higher-order harmonics in the ground leakage current. The steady-state and the dynamic performances of the proposed power converter during grid-connected mode of operation is assessed with simulation studies and are validated with experimental results.

Controllable Transmission Switch Based on Asymmetric Coupled Nonlinear Resonances

We explore the design and implementation of a passive reconfigurable switch based on nonlinear Fano resonators asymmetrically coupled to two ports. It was recently shown that asymmetric nonlinear resonators could provide passive bias-free nonreciprocal transmission when they were excited only from one port at a time. Here, we show that, by suitably exploiting time-reversal symmetry, this class of devices can also lead to controllable transmission routing, whereby a low-power pulse injected from one port controls the transmission of a larger power signal injected from the opposite port. This effect can be used to realize a power- and/or phase-controlled transmission switch with minimal power consumption. We first analyze the device with a circuit model to gain physical insights into its operation and to establish optimal operation conditions. We then provide a proof-of-principle experimental demonstration, reporting a device whereby the transmission of a 20-dBm signal can be switched from about 10% to 40% by controlling either the power or phase of a signal about 10 times weaker. This work demonstrates an alternative way to develop low-energy power-controlled reconfigurable switches for applications ranging from radar technology to wireless communications.

Modular Multilevel Resonant DC Transformer With Inherent Balancing Capability

As the demand for dc/dc converters in medium voltage applications is increasing in recent years, more and more attention has been paid to modular multilevel technology to reduce device stress. Derived from modular multilevel converter and LLC converter, this paper proposes a modular multilevel resonant dc transformer. Compared with the multi-stack structures, the proposed dc transformer has a simpler single-stack structure, which reduces the number and cost of sub-modules (SMs). Moreover, through the co-design of the boost inductor and the transformer, the proposed scheme can realize zero voltage switching of the primary switches and zero current switching of the secondary rectifier. With circulant modulation, not only a flexible step-down ratio is obtained, but also the SM capacitor voltages can be self-balanced without adding the control complexity. In addition, a high operating frequency is synthesized through a low switching frequency of the SM, thereby reducing the size of passive components and switching losses. The operating principle and theoretical analysis of the dc transformer are presented. A downscaled hardware prototype is built, and experimental results validate the correctness of the theoretical analysis and the feasibility of the converter.

Reactive Power Control and SVG Coordinated Control Method for HVDC Transmission System

This paper proposes a reactive power and SVG coordinated control method for a HVDC transmission system. The method includes calculating the reactive power ΔQ exchanged between the converter station and the AC system. Set the dead zone range of ΔQ and limit the output of ΔQ. Set the restriction condition of SVG’s ability to adjust and judge whether the reactive power emitted by SVG is restricted. Based on whether the reactive power sent by the SVG is limited and the limitation results of ΔQ, the input of the PI controller in the QPC module is calculated to complete the reactive power, and SVG coordinated control process. When this control method is adopted, the operating time of the converter greater than the rated angle is significantly reduced, the loss of the converter is effectively reduced. Meanwhile, the DC voltage rise and fall are stabilized, and the AC voltage fluctuations due to the passive switching are greatly reduced.

Interplay of bound states in the continuum empowers spectral-lineshape manipulation in all-dielectric metasurfaces

The bound states in the continuum (BICs) in optical metasurfaces have latterly received prominent attention for their ultrahigh quality factors and the promise that they hold for realizing lowthreshold nanolasers, high-harmonic generation, and slow-light devices. In this scenario, the flexible tuning of the BIC is at the heart of multifunctional and tunable metadevices underpinning the central role in the modulation of optical spectral responses. Most BIC-inspired works are limited to single types of BICs modes only affected by the structural perturbation without tunable functionality, while different types of BIC modes have received little attention in manipulating the spectral line shapes in optical metasurface. Here, we show that the simultaneous generation and tailored interplay of two types of BIC modes can empower the realization of tailorable spectral lineshape manipulation in all-dielectric metasurfaces. In particular, the magnetic symmetry-protected BICs and accidental BIC result from the preserved reflection symmetry and geometrical parameter perturbation, respectively. The varied asymmetric parameters and the polarization angle of the incident light are responsible for the generation and interplay of the symmetry-protected and accidental quasi-BIC modes. Additionally, the interplaying quasi-BICs enable the implementation of the dual-wavelength passive optical switches throughout the related telecom bands, and can exhibit the tunable spectral features of different types of Fano resonances and EIT analog-based slow-light effect. These results could offer exploration potential for the development of multifunction and high-performance metadevices.

The numerical study of multi-tube passive convective heat switches

Heat switches are widely used in cryogenic systems, playing an important role in controlling thermodynamic cycles and accelerating the cooling of cryogenic components. Among them, the convective heat switch, normally made from two identical tubes, realizes the on/off state by the presence/absence of a natural convective gas loop, which can be used to shorten the cooling time of cryogenic systems. In order to further understand the heat transfer mechanism of the passive convective heat switch, three-dimensional steady-state models of twin-tube and triple-tube configurations are established in this paper. The simulations of the twin-tube heat switch with different hot-end heat loads and different charge pressures are conducted and compared with the experimental results. The influence of the asymmetry of two tubes on thermal conductance is analyzed. Meanwhile, the simulation and comparison of twin-tube and triple-tube convective heat switches with equal void volume are carried out. It is found that the convective heat transfer performance of the twin-tube heat switch is slightly better than the triple-tube configuration, and when the cold-end temperature is 4 K and the hot end is applied 0.3 W heat load, the hot-end temperature is stable at 11.57 K, leading to a thermal conductance of 39.4 mW/K.

An Intelligent Rehabilitation Robot With Passive and Active Direct Switching Training: Improving Intelligence and Security of Human–Robot Interaction Systems

An Intelligent Rehabilitation Robot With Passive and Active Direct Switching Training: Improving Intelligence and Security of Human–Robot Interaction Systems