Low Power Consumption Devices Research Articles

Dual bit control low-power dynamic content addressable memory design for IoT applications

The Internet of things (IoT) is an emerging area in the semiconductor industry for low-power and high-speedapplications. Many search engines of IoT applications require low power consumption and high-speed content addressablememory (CAM) devices for the transmission of data packets between servers and end devices. A CAM is a hardwaredevice used for transfer of packets in a network router with high speed at the cost of power consumption. In this paper,a new dual bit control precharge free (PF) dynamic content addressable memory (DCAM) has been introduced. Theproposed design uses a new charge control circuitry, which is used to control the dual DCAM cell to get the match lineoutput for match/miss. Elimination of the precharge phase before the evaluation phase allows the proposed design toperform more search operations within the evaluation time. The proposed 64-bit PF-DCAM design is implemented usinga CMOS 45-nm technology node and Monte Carlo simulations are performed for power and search delay validation. Thesimulation results show that the proposed design reduces power and search delay when compared to conventional DCAMdesigns.

Dataset of the Optimization of a Low Power Chemoresistive Gas Sensor: Predictive Thermal Modelling and Mechanical Failure Analysis

Over the last few years, employment of the standard silicon microfabrication techniques for the gas sensor technology has allowed for the development of ever-small, low-cost, and low-power consumption devices. Specifically, the development of silicon microheaters (MHs) has become well established to produce MOS gas sensors. Therefore, the development of predictive models that help to define a priori the optimal design and layout of the device have become crucial, in order to achieve both low power consumption and high mechanical stability. In this research dataset, we present the experimental data collected to develop a specific and useful predictive thermal-mechanical model for high performing silicon MHs. To this aim, three MH layouts over three different membrane sizes were developed by using the standard silicon microfabrication process. Thermal and mechanical performances of the produced devices were experimentally evaluated, by using probe stations and mechanical failure analysis, respectively. The measured thermal curves were used to develop the predictive thermal model towards low power consumption. Moreover, a statistical analysis was finally introduced to cross-correlate the mechanical failure results and the thermal predictive model, aiming at MH design optimization for gas sensing applications. All the data collected in this investigation are shown.

Scientometric analysis of literature on distributed vehicular networks : VOSViewer visualization techniques

The idea of vehicular communication has evolved dramatically over the past two decades apparently with technological advancements that accord low power and memory consumption devices, and yet providing low latency and high performing abilities. In the 20th century, vehicular communications were primarily done through singling blinkers, tail lights, and hazard lamps, essentially serving rudimentary purposes. In the early 2000s, the term “VANET” was first introduced for demonstrating road safety and navigation. By the end of 2012, the term vehicle-to-everything(V2X) was coined with IEEE 802.11p as the supporting standard for underneath technology. The adequately increasing publications and development of VANET simulators like SUMO acknowledge the fact that there has been an intriguing interest in vehicular research. While publications are increasing massively in numbers, perhaps, we identified a lack of comprehensive scientometric analysis for this field. This paper aims at analyzing the researches carried out between 2009 and 2020 using Scopus data with a scientometric approach thereby highlighting the citation patterns and indulging journals, authors, institutes, countries in the field of vehicular communication. Furthermore, keywords analysis is also staged using VOSViewer to visualize the research patterns. This paper also tries to classify the publications into distinct clusters so formed in VOSViewer using classifying techniques, hence, to make the voluminous data acumen for the publication stride.

Security in ZigBee networks

When people start using home automation, they always feel the control of the home first: they believe that the future is now, and their application will be their console for life and do not pay attention to what they are losing. And suddenly the switch no longer works? After coming home at night, you have to pull out the phone, open the application, allow it to connect, and finally turn on the light. You can solve this problem with a presence sensor. Luminaires must work both with a switch (or button) at the entrance to the room and through a presence detector. Home automation should be compatible with the current workflow, not replace it. The only interface that can be more convenient and accessible to visitors of all ages is the voice interface. Take, for example, Apple: the only way to manage your HomeKit devices is Siri. Amazon has taken another step forward with Amazon Echo by providing a connected speaker/microphone that always listens. Voice interfaces are also not perfect. Command processing speed is low because you have to wait for an answer. There are also issues with command visibility, accent recognition, and cloud dependency for processing your voice. Good home automation is never annoying, it works unnoticed. Every year the interest in IoT grows, as various solutions appear on the market, differing in price, ecosystem and protocols used. One of the most popular smart home protocols today is Zigbee. Although ZigBee has been designed with security in mind, trade-offs have been made to ensure low cost, low power consumption and high device compatibility. For example, using the same encryption keys at different OSI levels of the same device. Such compromises inevitably lead to security risks. The aim of the article is to study the main security models of ZigBee and the shortcomings of network security.

A Survey of Energy and Spectrum Harvesting Technologies and Protocols for Next Generation Wireless Networks

Energy harvesting (EH) and spectrum harvesting (SH) are two promising and useful green communication and networking mechanisms for the next-generation wireless networks. While the former techniques exploit ambient energy sources to scavenge energy, the latter exploit the unused or moderately used electromagnetic spectrum. With the advent of cyber-physical systems and the Internet-of-Things (IoT), the presence of tens of billions of low power sensor devices would soon be a reality. These small sensing devices would be present in many systems around us, such as home appliances, telecommunication devices, medical electronics, transport systems, etc. These miniaturized, low-power consuming devices may exploit EH and SH techniques for energy storage and communication. These EH-SH-enabled sensors or low-power nodes need to consume very little energy for sensing and communicating opportunistically. However, several theoretical problems and practical challenges exist in EH-SH communications. In this comprehensive survey paper, we first present the historical background of EH, and SH techniques, and their development over several decades. Specifically, we focus on EH-SH communication technologies and protocols for a wide range of systems and networks. We present a detailed survey of the various harvesting techniques and protocols from recent literature. Finally, we describe exciting open, intra-disciplinary, and inter-disciplinary challenges for further research on EH-SH communication technologies.

Chiral Spin Spirals at the Surface of the van der Waals Ferromagnet Fe3GeTe2.

Topologically protected magnetic structures provide a robust platform for low power consumption devices for computation and data storage. Examples of these structures are skyrmions, chiral domain walls, and spin spirals. Here, we use scanning electron microscopy with polarization analysis to unveil the presence of chiral counterclockwise Néel spin spirals at the surface of a bulk van der Waals ferromagnet Fe3GeTe2 (FGT) at zero magnetic field. These Néel spin spirals survive up to FGT’s Curie temperature of TC = 220 K, with little change in the periodicity p = 300 nm of the spin spiral throughout the studied temperature range. The formation of a spin spiral showing counterclockwise rotation strongly suggests the presence of a positive Dzyaloshinskii–Moriya interaction in FGT, which provides the first steps towards the understanding of the magnetic structure of FGT. Our results additionally pave the way for chiral magnetism in van der Waals materials and their heterostructures.

AIN-Based MEMS (Micro-Electro-Mechanical System) Hydrophone Sensors for IoT Water Leakage Detection System

There is an urgent need for industrial Internet of things (IoT) solutions to deploy a smart hydrophone sensor grid to monitor pipeline health and to provide an accurate prediction in the event of any leakage. One solution is to develop an IoT water leakage detection system consisting of an interface to capture acoustic signals from aluminum nitride (AlN)-based micro-machined infrasonic hydrophone sensors that are fed as inputs and predict an approximate leak location as a form of output. Micro-electro-mechanical systems (MEMS) are particularly useful for IoT applications with low power consumption and small device footprint. Data analytics including characterization, pre/post processing are applied to determine the leaks. In this work, we have developed the process flow and algorithm to detect pipe leakage occurrence and pinpoint the location accurately. Our approach can be implemented to detect leaks for different pipe lengths, diameters and materials.

Electromechanical Modeling of Vibration-Based Piezoelectric Nanogenerator with Multilayered Cross-Section for Low-Power Consumption Devices

Piezoelectric nanogenerators can convert energy from ambient vibrations into electrical energy. In the future, these nanogenerators could substitute conventional electrochemical batteries to supply electrical energy to consumer electronics. The optimal design of nanogenerators is fundamental in order to achieve their best electromechanical behavior. We present the analytical electromechanical modeling of a vibration-based piezoelectric nanogenerator composed of a double-clamped beam with five multilayered cross-sections. This nanogenerator design has a central seismic mass (910 μm thickness) and substrate (125 μm thickness) of polyethylene terephthalate (PET) as well as a zinc oxide film (100 nm thickness) at the bottom of each end. The zinc oxide (ZnO) films have two aluminum electrodes (100 nm thickness) through which the generated electrical energy is extracted. The analytical electromechanical modeling is based on the Rayleigh method, Euler–Bernoulli beam theory and Macaulay method. In addition, finite element method (FEM) models are developed to estimate the electromechanical behavior of the nanogenerator. These FEM models consider air damping at atmospheric pressure and optimum load resistance. The analytical modeling results agree well with respect to those of FEM models. For applications under accelerations in y-direction of 2.50 m/s2 and an optimal load resistance of 32,458 Ω, the maximum output power and output power density of the nanogenerator at resonance (119.9 Hz) are 50.44 μW and 82.36 W/m3, respectively. This nanogenerator could be used to convert the ambient mechanical vibrations into electrical energy and supply low-power consumption devices.

Ferroelectric-Modulated MoS2 Field-Effect Transistors as Multilevel Nonvolatile Memory.

Ferroelectric field-effect transistors (FeFETs) with semiconductors as the channel material and ferroelectrics as the gate insulator are attractive and/or promising devices for application in nonvolatile memory. In FeFETs, the conductivity states of the semiconductor are utilized to explore the polarization directions of the ferroelectric material. Herein, we report FeFETs based on a few layers of MoS2 on a 0.7Pb(Mg1/3Nb2/3)O3-0.3PbTiO3 (PMN-PT) single crystal with switchable multilevel states. It was found that the On-Off ratios can reach as high as 106. We prove that the interaction effect of ferroelectric polarization and interface charge traps has a great influence on the transport behaviors and nonvolatile memory characteristics of MoS2/PMN-PT FeFETs. In order to further study the underlying physical mechanism, we have researched the time-dependent electrical properties in the temperature range from 300 to 500 K. The separation of effects from ferroelectric polarization and interfacial traps on electrical behaviors of FeFETs provides us with an opportunity to better understand the operation mechanism, which suggests a fantastic way for multilevel, low-power consumption, and high-density nonvolatile memory devices.

Ultra-Wideband Technology: Standards, Characteristics, Applications

The boost in the number of mobile users and automated devices has led to urge of high speed communication with low power consumption devices. Another demand is the uninterrupted communication. This has led to the evolution of a technique referred as Ultra Wideband (UWB). UWB is capable of providing very high data rates and has very low power consumption. This technique relies on carrier less transmission of data in the form of pulses over a wide bandwidth and is mainly suited for short range applications. The short pulses add to the robust performance in the presence of multipath effects. Low spectral power density permits amalgamation of multiple signals and also interception. Due to numerous benefits, UWB finds it usefulness in many areas such as wireless communication, radar imaging, medical and indoor positioning. The paper aims to provide an overview of UWB standards, characteristics and applications.

Effects of Charge Trapping at the MoS2–SiO2 Interface on the Stability of Subthreshold Swing of MoS2 Field Effect Transistors

The stability of the subthreshold swing (SS) is quite important for switch and memory applications in logic circuits. The SS in our MoS2 field effect transistor (FET) is enlarged when the gate voltage sweep range expands towards the negative direction. This is quite different from other reported MoS2 FETs whose SS is almost constant while varying gate voltage sweep range. This anomalous SS enlargement can be attributed to interface states at the MoS2–SiO2 interface. Moreover, a deviation of SS from its linear relationship with temperature is found. We relate this deviation to two main reasons, the energetic distribution of interface states and Fermi level shift originated from the thermal activation. Our study may be helpful for the future modification of the MoS2 FET that is applied in the low power consumption devices and circuits.

Preparation of Efficient Memristive Films (2D materials) for Flexible Devices and Their Electrical Characterisation

2D materials have various properties which make them potential candidates for better applications in electronic, chemical and biosensing devices. It is certain that so much work have previously been done on 2D materials. However, the aim of this study is to fabricate a material with a better quality that could create room for greater opportunities in electronic, chemical and biosensing devices. This fabrication was performed through exfoliation, and wet chemical means or PVD layer deposition technique. Furthermore, the current state of the electronics industry has necessitated the need for a novel and suitable memory for low cost and large scale flexible electronics materials. These materials should be non-volatile and low-power consuming devices because energy is of global concern. The non-volatility nature and the energy consuming ability of the finally fabrication was investigated from the current vs time curve in order to obtain the energy retention time. After the fabrication of the electronics material, various characterisations were performed on the devices; stability and endurance level was tested from the current vs cycle numbers of the curves. The rationale for these experiments is to take advantage of the Van der Waals multilayer force present in-between the layers of the two-dimensional (2D) materials to form a material with a desirable atomic and accurate quality. The outcome shows improve 2D memeristive material required to address most challenges experienced by electronic devices, particularly in the multilayer thin film. The result shows performance improvement of the memristors by raising the switching endurance at an elevated temperature of 300 oC and above. Finally, the mechanical flexibility and stability together with its endurance level were tested.

VOCs Detection Employing Graphene Loaded with Perovskite Nanocrystals

Introduction Despite graphene shows outstanding electronic and physicochemical properties to be employed as a gas sensor, its implementation in commercial devices still faces many issues. The main drawbacks that are limiting real applications are the low sensitivity and selectivity towards gas molecules of graphene in its pristine form. In consequence, further modifications are needed to enhance these essential gas-sensing parameters. One of the easiest and most effective strategies is the decoration of graphene (or other carbon nanomaterials) with metal or metal-oxide nanoparticles [1], an approach that has been extensively studied by many researchers.In contrast, perovskites are promising materials that despite showing rich surface chemistry have attracted limited research interest for gas sensing until now. Probably because of their inherent problems, such as high degradation in contact with ambient moisture or their stability problems even at moderate working temperatures. Nevertheless, we recently reported the first use of graphene loaded with perovskite nanocrystals [2] to detect NO2 and NH3. Our approach has been demonstrated as a novel option to employ perovskites in dry and humid air, instead of their use in inert atmospheres by employing nitrogen without ambient moisture [3]. Here we deepen our study by analyzing, for the first time, a wide range of perovskite-graphene hybrids for gas sensing. Methods Chemical-sensitive films composed by graphene nanolayers loaded with different perovskite nanocrystals are developed. In particular, five different perovskite nanocrystals are synthesized and studied. Considering the general formula of perovskites (ABX3 ), we started with the perovskite nanocrystal already employed as a gas sensor in our previous work, which is MAPbBr3 (1). Thus, as our main objective is to analyze the effect on the gas sensing properties of the different elements in perovskites, first we change the cation A, obtaining two different perovskites with caesium (CsPbBr3) (2) and formamidinium (FAPbBr3) (3). After that, two new nanocrystals are obtained by changing the anion X, replacing the bromide by iodine (MAPbI3) (4) and chlorine (MAPbCl3) (5). Different synthesis processes are performed to obtain the five nanocrystals, but all of them show diameters below to 10 nm, which are found suitable for the decoration of graphene. Characterization All the nanomaterials employed in this work are characterized in depth employing techniques such as X-Ray Photoelectron Microscopy (XPS) to obtain detailed information about the graphene functional groups; High-Resolution Transmission Electron Microscopy (HR-TEM) to analyze the nanocrystal size and its interplanar distances; Field Emission Scanning Electron Microscope (FESEM) to evaluate the spatial nanocrystal distribution over the graphene nanolayers; and finally, an X-Ray Diffraction (XRD) analysis to study the crystalline structure of perovskites. Afterwards, the films developed are integrated in gas sensing devices, which are placed in an airtight Teflon chamber connected to calibrated bottles of nitrogen dioxide, ammonia, benzene and toluene. Consecutive gas dilutions are performed in order to obtain different analyte concentrations. With these results, the effect of the cation and anion in the detection of pollutant gases and vapors was studied at low concentrations. Full details will be given at the conference. Results and Conclusions The resulting hybrid nanomaterials, i.e. graphene loaded with perovskite nanocrystals have been demonstrated as great options for room-temperature operated gas sensing, entailing to low-power consumption devices. Additionally, the high instability of perovskites over time is clearly ameliorated here, thanks to the highly hydrophobic character of graphene, which protects the nanocrystals from the effect of ambient moisture. As a result, we can take advantage of the outstanding perovskite properties by increasing the stability and the sensor shelf-life. Also, sensitive, reproducible, reversible and remarkably stable responses to nitrogen dioxide, ammonia and VOCs can be obtained (see Figure 1) for sensors operated room temperature. Even, higher sensitivity can be obtained to both, electron donor and electron-withdrawing gases, thanks the presence of perovskite nanoparticles in comparison to their bare graphene counterparts. The reason probably is because perovskites can act as ambipolar charge transporters. These results will allow a better understanding about the role in the sensing mechanism of the different perovskite components, and constitutes a novel approach to employ perovskites in gas sensors, showing a high potential to improve the performance of other usual graphene decorations. For instance, despite the good results reported by loading graphene with metal oxides, usually these are associated with high cost (derived from the use of noble metals) and high working temperatures. Conversely, the decoration of graphene with perovskite nanocrystals opens a new low-cost production concept linked to low-power consumption devices.

A Method for Human Facial Image Annotation on Low Power Consumption Autonomous Devices.

This paper proposes a classifier designed for human facial feature annotation, which is capable of running on relatively cheap, low power consumption autonomous microcomputer systems. An autonomous system is one that depends only on locally available hardware and software—for example, it does not use remote services available through the Internet. The proposed solution, which consists of a Histogram of Oriented Gradients (HOG) face detector and a set of neural networks, has comparable average accuracy and average true positive and true negative ratio to state-of-the-art deep neural network (DNN) architectures. However, contrary to DNNs, it is possible to easily implement the proposed method in a microcomputer with very limited RAM memory and without the use of additional coprocessors. The proposed method was trained and evaluated on a large 200,000 image face data set and compared with results obtained by other researchers. Further evaluation proves that it is possible to perform facial image attribute classification using the proposed algorithm on incoming video data captured by an RGB camera sensor of the microcomputer. The obtained results can be easily reproduced, as both the data set and source code can be downloaded. Developing and evaluating the proposed facial image annotation algorithm and its implementation, which is easily portable between various hardware and operating systems (virtually the same code works both on high-end PCs and microcomputers using the Windows and Linux platforms) and which is dedicated for low power consumption devices without coprocessors, is the main and novel contribution of this research.

Design of Low Noise Amplifier for WLAN using pHEMT

The low power consumption devices are frequently focused in design and manufacturing wireless communication system. This paper gives a systematic design of a low noise amplifier for WLAN application aimed to obtain minimum noise figure. The simulation result shows that the noise figure is in the appreciable level (1.67 dB). The maximum gain is greater than 10 dB. These are the predominant requirements of an LNA. Also it posses good stability and the LNA design uses pHEMT for its appreciable noise performance. Â

Interfacial Dzyaloshinskii-Moriya interaction between ferromagnetic insulator and heavy metal

Recent demonstration of the interfacial Dzyaloshinskii-Moriya interaction (DMI) between a heavy metal and a magnetic insulator provides the possibility to manipulate chiral spin textures in the magnetic insulator for the extremely low power consumption devices. However, the origin and strength of the interfacial DMI remain in dispute in this system. We used the electrical transport measurements to determine the DMI strength to be ∼0.040 pJ/m at room temperature in Pt/Tm3Fe5O12 (TmIG) bilayers. The TmIG saturation magnetization and DMI strength exhibit different temperature dependences, which is attributed to the DMI being mainly contributed by Fe ions instead of Tm ions. With a Cu layer inserted between Pt and TmIG, the DMI strength is reduced to ∼0.012 pJ/m and the topological Hall effect vanishes, strongly suggesting that the Pt/TmIG interface has important contribution to the DMI.

Scavenging vibrational energy with a novel bistable electromagnetic energy harvester

Harvesting energy from mechanical vibrations via nonlinear energy harvesters has been considered as an effective approach for permanently powering embedded devices and sensors. Many previous studies focused on nonlinear piezoelectric energy harvesters based on cantilever beam structures. This paper presents a novel bistable electromagnetic energy harvester (BEEH) with several permanent magnets (PMs). The bistability is achieved by designing the interaction between magnetic repulsive and attractive forces. The shape of potential wells can be changed by adjusting the distance among the PMs. The theoretical model of the BEEH is established and the analytical solutions are obtained by using the harmonic balance method. The effects of the excitation frequency, excitation amplitude, resistance and shape of potential wells on the energy harvesting performance of the BEEH are investigated numerically and experimentally. The results show that the proposed BEEH has a wide operating bandwidth and high energy harvesting efficiency. The output power can reach up to 28 mW, which is able to power up some low-power consumption devices.

Low-Power, Large-Area and High-Performance CdSe Quantum Dots/Reduced Graphene Oxide Photodetectors

Graphene has unique and outstanding properties that make it a promising material for many applications. It has triggered considerable research in fields including solar cells, photodetectors, electrodes, and supercapacitors. Despite the favorable characteristics of devices using graphene have been widely explored, issues such as low absorbance, complex processing, and limited device size remain. Hence, we present large-area CdSe quantum dots (QDs)/reduced graphene oxide (rGO) films and corresponding photodetectors through a cost-effective and simple spin-coating method. As light turns on, CdSe QDs are excited and generate excess electron-hole pairs, leading to a significantly increased on/off current ratio of 2195 at a low bias voltage of -1 V, compared to that of photodetectors without CdSe QDs. Decorating the rGO film with CdSe QDs enables the wavefunction modulation and enhances the light harvesting. Our proposed high-performance photodetector can be operated at a low voltage, which is beneficial for applications in various green and low-power consumption devices.

A cathode interface engineering approach for the comprehensive study of indoor performance enhancement in organic photovoltaics

Organic photovoltaics (OPVs) have a promising future in reliable energy harvesting to drive low power consumption devices for indoor applications.

A hybrid wind energy harvester using a slotted cylinder bluff body

Harvesting energy from wind to supply low-power consumption devices has attracted numerous research interests in recent years. However, a traditional vortex-induced vibration energy harvester can only operate within a limited range of wind speed. Thus, how to broaden the effective wind speed range for energy harvesting is a challenging issue. In this paper, a slotted cylinder bluff body is proposed for being used in the design of a wind energy harvester. The physical prototype is manufactured and the wind tunnel test is performed for evaluating the actual performance of the prototyped energy harvester. The effect of the orientation of the slot on the performance of the proposed energy harvester is experimentally investigated. As compared to the traditional counterpart without the slot at the lateral side of the bluff body, the proposed energy harvester demonstrates the superiority for realizing broadband energy harvesting. Due to the introduction of the slot, and by carefully tuning the orientation of the slot, both the vortex-induced vibration and the galloping phenomena can be stimulated within two neighboring wind speed ranges, leading to the formation of an extremely broad bandwidth for energy harvesting.