Hasil untuk "Electric apparatus and materials. Electric circuits. Electric networks"

Sooyoung Oh, Wonryeol Lee, Sun K. Hong

As the applications utilizing harmonic backscattering continue to expand, the works on analyzing the radar cross section (RCS) through harmonic radar equation have also gained attention. Although various approaches exist for deriving harmonic RCS, there remains a gap in the theoretical derivation and experimental validation of the radar equation that accurately accommodates the specific harmonic responses of a given nonlinear target. This paper introduces a comprehensive radar modeling approach designed for practical harmonic radar system development. A mathematical model of reference harmonic radar system is proposed, which precisely takes into account the harmonic responses from a reference target engineered with a circuit simulation. To validate the effectiveness of this approach, two experimental scenarios are conducted, demonstrating that the proposed approach can be applied to harmonic radar models. Furthermore, this method enables the radar designers to systematically adjust radar parameters based on specific target characteristics and operational requirements.

Swati Agarwal, Ranjana Sodhi

Nawel Meftah, Badreddine Ratni, Mohammed Nabil El Korso et al.

Abstract Due to its growing importance and wide range of applications, direction‐of‐arrival (DOA) estimation has become a major research topic, particularly in the field of communication systems. While traditional DOA estimation methods rely on antenna arrays and complex algorithms, recent progress achieved in the design and implementation of metasurfaces has proved their effectiveness as promising alternatives. This study presents a distinct approach for DOA estimation that combines the use of a programmable metasurface with deep learning. The programmable metasurface together with a radio‐frequency power detector placed at the focal point, acts as a parabolic reflector antenna with an adjustable pointing direction, which scans the azimuth plane in 5° increments to receive the power level of incoming signals. The collected data is then fed into a pre‐trained multilayer neural network to enable DOA estimation with a resolution of lower than 1° without requiring fine‐tuning of the scanning procedure. This approach ensures accurate and fast estimations, paving the way for advanced solutions in detection and localization for various applications.

Jorge A. Cardenas, Laura C. Merrill, Alexis Maurel et al.

Additive manufacturing (AM) processes, like 3D printing, help to facilitate complex and customizable battery geometries which can provide design freedom and enhance volumetric energy density within electronic devices. AM materials must have the thermal and mechanical properties that enable printability, and when used in batteries, AM materials must also be chemically and electrochemically compatible with the battery chemistry. The compatibility between AM materials and the battery is of particular importance for the cell packaging materials which must be inert and are often overlooked. This study systematically studies AM-compatible polymeric materials for use as gaskets in lithium-ion cells. The materials investigated include three thermoplastics suitable for material extrusion printing: polylactic acid (PLA), polycarbonate, and polypropylene/polyethylene copolymer (PPPEC); and two photoresins suitable for vat photopolymerization (VPP) printing: an acrylate-based photoresin and a polyethylene glycol diacrylate photoresin. The AM gasket materials were tested in comparison to a conventional commercial polypropylene gasket. Mechanical testing (swell measurements and material stiffness) and electrochemical testing (linear sweep voltammetry and galvanostatic cycling of full cells) demonstrated that PLA and the VPP polymers were the least compatible with the lithium-ion battery chemistry, despite their prevalent use in studies of AM batteries, and that PPPEC was the most compatible.

Finn Dobschall, Hauke Hartmann, Sophia Caroline Bittinger et al.

Abstract In this study, the mechanical properties of freestanding membranes made of graphene oxide (GO), titania nanorods (TNRs), and silk fibroin (SF) are investigated and their application is demonstrated as electrostatically driven actuators. Using a stamping process, the membranes are transferred onto substrates with circular apertures or square cavities measuring ∼80 to 245 µm in diameter or edge length, respectively. Afterwards, the membranes are exposed to deep‐UV (DUV) radiation in order to photocatalytically convert GO to reduced graphene oxide (rGO). Microbulge tests combined with atomic force microscopy (AFM) measurements reveal enhanced mechanical stability after the DUV treatment, as indicated by an increase of Young's modulus from ∼22 to ∼35 GPa. The toughness of the DUV‐treated membranes is up to ∼1.25 MJ m−3, while their ultimate biaxial tensile stress and strain are in the range of ∼377 MPa and ∼0.68%, respectively. Further, by applying voltages of up to ±40 V the membranes are electrostatically actuated and deflected by up to ∼1.7 µm, as determined via in situ AFM measurements. A simple electrostatic model is presented that describes the deflection of the membrane as a function of the applied voltage very well.

Arash Ghobadi, Cherian J. Mathai, Jacob Cook et al.

Abstract Reducing the Schottky barrier height and Fermi level de‐pinning in metal‐organic semiconductor contacts are crucial for enhancing the performance of organic transistors. The reduction of the Schottky barrier height in bottom‐contact top‐gate organic transistors is demonstrated by adding 1 nm thick atomic layer deposited Al2O3 on the source and drain contacts. By using two different donor‐acceptor copolymers, both p‐ and n‐type transistors are investigated. Temperature‐dependent current–voltage measurements from non‐treated, self‐assembled monolayer treated, and Al2O3 treated Au source‐drain contact field‐effect transistors with varying channel lengths are carried out. The drain current versus drain voltage near zero gate voltage, which may be described by the thermionic emission model at temperatures above 150 K, allows the estimation of the Schottky barrier height (φB). The Al2O3 contact‐treated transistors show more than 40% lower φB compared with the non‐treated contacts in the p‐type transistor. Similarly, an isoindigo‐based transistor, with n‐type transport, shows a reduction in φB with Al2O3 treated contacts suggesting that such ultrathin oxide layers provide a universal method for reducing the barrier height.

Federico Prescimone, Wejdan S. AlGhamdi, Giulia Baroni et al.

Abstract Within multijunction organic and hybrid photodetectors (PDs), organic and hybrid phototransistors (HPTs) hold promises for high sensitivity (S) and specific detectivity (D*). However, it is difficult to achieve a trade‐off between a large sensing area, a fast response, and a high D*. Here, we propose an alternative phototransistor concept relying on a geometrically engineered tri‐channel (Tr‐iC) architecture with a 4‐mm2 large sensing area, applied to a multilayer HPT whose active region is comprised of an inorganic In2O3/ZnO n‐type field‐effect channel and solution‐processed organic bulk heterojunction (BHJ) or hybrid perovskite light‐sensing layer. The resulting HPTs combine a responsivity (R) up to 105 A/W, thanks to the efficient charge transport (at the bottom In2O3/ZnO layer) and a D* estimated at 1015Jones, which allows to measure low light power densities down to 10 nW cm−2. These figures of merit are coupled to a fast response (risetime <10 ms and falltime of ≈100 ms for illumination, in the µW/cm2 range), which is comparable to the time‐response of organic PDs in a diode architecture. The experimental data are supported by a comprehensive device modeling, which helps highlighting the peculiar advantages of the proposed large area, Tr‐iC, and multilayer HPT architecture.

Yulei Han, Yunpeng Guo, Zeyu Li et al.

The layer Hall effect is an intriguing phenomenon observed in magnetic topological layered materials, where the Hall response arises from the opposite deflection of electrons on top and bottom layers. To realize layer Hall effect, space-time $\mathcal{PT}$ symmetry is typically broken by applying an external electric field. In this work, we propose a new mechanism to realize the layer Hall effect by introducing inequivalent exchange fields on both surfaces of a topological insulator thin film, in the absence of an electric field. This approach yields a distinct Hall response compared to the conventional electric-field-induced layer Hall effect, particularly with respect to the Fermi level. Taking the topological insulator Sb$_2$Te$_3$ as a concrete example, we demonstrate the feasibility of inducing the layer Hall effect only by coupling the top and bottom surfaces of Sb$_2$Te$_3$ with different magnetic insulators. Notably, we show that both built-in electric-field-induced and inequivalent exchange-fields-induced layer Hall effects can be achieved by tuning the stacking order between Sb$_2$Te$_3$ and the magnetic layers. Given the well-established experimental techniques for fabricating topological insulator thin films, our work offers a viable pathway for realizing layer Hall effect without external electric field.

Ali Ehsan, Robin Preece

Yagmur Ceren Alatas, Uzay Tefek, Burak Sari et al.

In electrical sensing applications, achieving a uniform electric field at the sensing region is required to eliminate the compounding effect of particle location on the signal magnitude. To generate a uniform electric field in a microfluidic platform, 3D electrodes based on conductive electrolyte liquids have been developed before, where the ionic conductivity of the electrolyte was sufficient for impedance measurements at low frequencies (typically lower than 50 MHz). However, electrolyte liquids cannot be used as electrodes at microwave frequencies (&gt;1 GHz) due to the low mobility of ions. Here, we used Galinstan, a room-temperature liquid metal, to microfabricate 3D liquid electrodes connected to a microwave resonator &#x2014; and all integrated within a microfluidic system. By generating a highly uniform electric field, a mixture of 20 &#x03BC;m and 30 &#x03BC;m diameter polystyrene particles were measured and analyzed without any calibration for particle position. The results demonstrate the utility of liquid electrodes in enhancing the electrical characteristics of microwave resonant sensors.

Chunfeng Zhang

With the continuous development of technology, music performances are gradually moving from the traditional stage format to the virtual reality (VR) environment to provide a more immersive experience for the audience. But traditional music performance lacks interaction and adaptability with the audience. This research aims to propose an adaptive matching optimization and VR system for indoor music performance based on wireless sensors to realize the interaction and self-adaptation between music performance and audience. The research uses wireless sensor networks to obtain audience behavior and feedback information, and matches it with music performance. By collecting physiological indicators such as the audience's movements, emotions and heartbeat, we can analyze and identify the audience's emotion and experience state in real time, so as to realize the adaptive music performance. The experimental results show that the adaptive music performance system based on wireless sensor successfully improves the audience's participation and emotional experience. The audience can interact with the musical performance through their movements and emotions, and feel a personalized musical experience that enables the audience to be more immersed and engaged.

Changjae Moon, Minsoo Choi, Myungguk Lee et al.

From the perspective of channel behaviors, we review several design techniques of resistive termination for wireline applications. Termination impedances strongly affect the channel behaviors. Their impacts vary a lot depending on the types of interconnects and the circuits. Therefore, termination impedances must be appropriately designed for the target applications. In this article, first, we explain an intuitive analytical transfer function model of wireline channels. The model allows designers to easily and intuitively understand the impacts of the termination resistances on the channel behaviors. Second, we review various resistive termination techniques for LC-dominant channels and discuss their design tradeoffs. Especially, we theoretically explain the relaxed impedance matching technique, which allows designers to violate impedance matching for design improvements at the cost of a negligible penalty in signal integrity. Third, we review various resistive termination techniques for RC-dominant channels and their design tradeoffs. We especially emphasize and theoretically explain why and how the design tradeoffs by resistive terminations in RC-dominant channels are different from the ones in LC-dominant channels.

Manvendra Chauhan, Sumit Choudhary, Satinder K. Sharma

Abstract Resistive random‐access memories (ReRAM) are promising candidates for next‐generation non‐volatile memory, logic components, and bioinspired neuromorphic computing applications. The analog resistive switching (RS) tuning with a sizable memory window is crucial for realizing multi‐level storage devices. This work demonstrates the multi‐level storage capability of fabricated Ag/NiO/W ReRAM architecture, controlled through voltage modulations. The fabricated ReRAM structures exhibit stable bipolar analog RS, non‐overlapping resistance, and endurance of ≈104 cycles, respectively, with marginal statistical variations/fluctuations. Also, the fabricated ReRAM offers highly controlled and stable retention characteristics tested up to ≈104 s with significantly controlled statistical variations/fluctuations. Adjacent thereto, it offers a substantially lower operating SET and RESET voltage of 1 and −1 V, respectively. Moreover, the non‐overlapping multiple resistive states are observed with the voltage pulse modulation schemes. Furthermore, the current switching mechanism is described using a model proposed for the conductive filament growth and the contribution of the NiO/W interface layer (IL) toward notable RS of fabricated Ag/NiO/W structures.

Md. Alamgir Hossain, Md. Saiful Islam

Distributed denial-of-service (DDoS) attacks pose a significant threat to computer networks and systems by disrupting services through the saturation of targeted systems with traffic from multiple sources. Real-time detection of these attacks has become a critical cybersecurity task. However, current DDoS attack detection methods suffer from high false positive rates and limited ability to capture the complex patterns of attack traffic. This research proposes an enhanced approach for detecting DDoS attacks using a hybrid feature selection technique in combination with an ensemble-based classifiers. The ensemble-based approach aggregates many decision trees to increase classification accuracy and reduce overfitting and model robustness. The feature selection technique uses correlation analysis, mutual information, and principal component analysis to identify the most useful characteristics for attack detection. The ensemble-based Random Forest classifier from the various ensemble-based approaches with the specified relevant features produces the best detection rates. Many datasets related to identifying DDoS attacks are used to evaluate the proposed model, and experimental findings demonstrate that it surpasses existing techniques in terms of accuracy, recall, precision, f1-score, and false positive rate, with other evaluation metrics. The proposed approach achieves almost 100 % accuracy, 100 % true positive rate, and 0 % error rate making it a promising solution for DDoS attack detection.

D. Sztenkiel, K. Gas, N. Gonzalez Szwacki et al.

We report magnetization changes generated by an electric field in ferromagnetic Ga$_{1-x}$Mn$_x$N grown by molecular beam epitaxy. Two classes of phenomena have been revealed. First, over a wide range of magnetic fields, the magnetoelectric signal is odd in the electric field and reversible. Employing a macroscopic spin model and atomistic Landau-Lifshitz-Gilbert theory with Langevin dynamics, we demonstrate that the magnetoelectric response results from the inverse piezoelectric effect that changes the trigonal single-ion magnetocrystalline anisotropy. Second, in the metastable regime of ferromagnetic hystereses, the magnetoelectric effect becomes non-linear and irreversible in response to a time-dependent electric field, which can reorient the magnetization direction. Interestingly, our observations are similar to those reported for another dilute ferromagnetic semiconductor Cr$_x$(Bi$_{1-y}$Sb$_y$)$_{1-x}$Te$_3$, in which magnetization was monitored as a function of the gate electric field. Those results constitute experimental support for theories describing the effects of time-dependent perturbation upon glasses far from thermal equilibrium in terms of an enhanced effective temperature.

Roozbeh Torkzadeh, Jeroen van Waes, Vladimir Ćuk et al.

Aniello Pelella, Daniele Capista, Maurizio Passacantando et al.

Abstract A photodetector with bias‐tuneable current is realized by adding a film of single‐walled carbon nanotubes (CNT), forming a CNT/Si3N4/Si capacitor, to a prefabricated Pt–Ti/Si3N4/Si metal–insulator–semiconductor (MIS) diode. Electrical characterization of the entire device is performed to extract the temperature‐dependent ideality factor and Schottky barrier height in the framework of the thermionic emission theory. The CNT/Si3N4/Si capacitor increases the reverse current of the parallel Pt–Ti/Si3N4/Si MIS diode by adding a Fowler–Nordheim tunneling current at high reverse voltage bias. This feature endows the photodetector with two different photocurrent levels, photoresponsivity up to 370 mA W−1 and external quantum efficiency up to 50% at 950 nm wavelength. The device also shows a different photoresponse when light is focused on the CNT/Si3N4/Si region or around the Pt–Ti/Si3N4/Si structure. The photodetector can also be used as an optoelectronic Boolean logic device, in which the applied voltage bias and the incident light are the two input signals, and the photocurrent is the output. Furthermore, light generates a photocurrent at zero voltage and a photovoltage at zero current, making the device a self‐powered photodetector.

S. Menaga, R. Vanithamani

The wireless body area network (WBAN) offers healthcare applications for remote patient monitoring. In healthcare, prioritizing patient data has a high impact on the energy usage, delays, and congestion involved in routing. Energy usage, battery life, and absorption rates are current research obstacles in WBAN. The path loss ratio and residual energy were generally the focus of attention during data transfer. Despite this, compromised transaction security caused serious problems with the delivery of vital health data. The Quantum Spider Cramer Shoup Public Key Cryptosystem (QS-CSPKC), which is proposed in this study, is an optimized priority-aware (for many patients) and transaction security technique for vital sensed data in WBAN, selects the optimum energy efficient and reliable path to assure secure data transfer. The proposed QS-CSPKC method employs Dual Contention Access Periods (DCAPs) for managing regular data (i.e., normal sensed or low priority data) and life-threatening data (i.e., abnormal sensed data or high priority data). After prioritizing, the Quantum Spider Monkey Optimized Routing algorithm is used to allocate an optimal shortest route for normal low priority data (i.e., with 0 as the quantum value) and an energy-efficient emergency route for critical high priority data (i.e., with 1 as the quantum value). In addition, to prevent illegal access during transmission, security keys are generated using the Cramer Shoup public key cryptosystem. By using this model, only legitimate users have access to information for which they are authorized. The evaluation results were validated through simulations, showing that the proposed QS-CSPKC method performs efficient routing and secure data transmission better than conventional techniques in terms of throughput, packet loss, average power consumption, and energy use.

Qi Song, Yu Zhou, Yifei Wang et al.

Abstract Due to the low photon energy in the relevant frequency band, fewer materials can directly excite carriers, and an extreme lack of high‐performance, large‐area detectors, limit the promotion, and development of 6G technology. In addition, flexible detectors with the integration of 6G communication and Internet of Things technology has good prospects for application in the development of optoelectronic devices, which are also urgently needed. A large‐area flexible thin layer terahertz detector is designed that combines the advantages of excellent optoelectronic performance in the detection of electromagnetic waves with low photon energy and the localized surface plasmon (LSP) effect in a sub‐wavelength structure detector. Due to the large effective area, the spiral electrode device demonstrates the best performance at room temperature. The noise equivalent power (NEP) and photoresponsivity (RV) are achieved with 0.4 pW Hz−1/2 and 154 MV W−1 at 0.28 THz. In addition, the bending experiments show that the device has extreme advantages for flexible 6G detector applications.

Kolahal Bhattacharya

In this work, we present an explanation of the electric charge quantization based on a semi-classical model of electrostatic fields. We claim that in electrostatics, an electric charge must be equal to a rational multiple of the elementary charge of an electron. However, the charge is quantized if the system has certain boundary conditions that force the wavefunction representing an electric field to vanish at specific surfaces. Next, we develop the corresponding model for the electric displacement vector. It is demonstrated that a number of classical results, e.g. bending of field lines at the interface of two dielectric media, method of images, etc. are all consistent with the predictions of this model. We also present the possible form of Gauss's law or (Poisson's equation), to find the wavefunctions of the field from a source charge distribution, in this model.