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

Zhi Shiuh Lim, Lin Er Chow, Khoong Hong Khoo et al.

Abstract Among the vast magnetic heterostructures explored in Condensed Matter Physics, two contrasting interpretations of the hump‐shaped Hall Effects remain ambiguous and debated, namely, the overlap of two opposite‐signed Karplus–Luttinger Hall loops associated with inhomogeneous collinear domains with perpendicular anisotropy, or the Geometrical/Topological Hall Effect emanated from hexagonal close‐packed lattice of Skyrmion ground state with smoothly varying non‐collinear moments. Their similarity in topology implies difficulty in discrimination via magnetic imaging. Here, this ambiguity is overcome and clarified by the divergence exponent of hump peak fields extracted from Hall measurements with magnetic field rotation on several heterostructures. Their difference in sensitivity to in‐plane fields reveals that the former mechanism involves higher uniaxial anisotropy than the latter, departing from the Skyrmion ground state regime by the Ginzburg–Landau framework of triple‐q spin‐wave superposition. Numerous material systems can be summarized into a single curve of divergence exponent versus the collinear quality factor, bridging the crossover of the two mentioned mechanisms.

Najmeh Zahabi, Igor Zozoulenko

Abstract Understanding charge carrier transport in conductive polymers is imperative for the materials' synthesis and optimizing devices. While most theoretical studies utilize time‐independent approaches for describing charge transport, there is an interest in addressing temporal charge carrier dynamics, which provides more information than time‐independent methods. In this study, ab initio molecular dynamics is utilized to gain microscopic insights into charge carrier temporal dynamics in PEDOT. It is demonstrated that transport along the chains is band‐like and across the chains is hopping‐like. Polaron mobility is calculated along the chains to be 4 cm2 V−1 s−1, providing a theoretical upper limit in thiophene‐based conducting polymers. Also, by tracing polaron jumps between chains, the hopping rate, aligning with Marcus' theory is extracted. If an electric field can release polarons from Coulomb traps is investigated, finding that the necessary field strength surpasses typical experimental values. Two regimes of intrachain polaron movement are found: under low/intermediate electric fields, polaron moves velocity‐constantly with coupled charge and lattice distortion, while under high electric fields, charge and lattice distortion decouple. The methodology applies to studying mobilities in p‐ and n‐doped conjugated polymers, including highly doped systems with more polymer chains, and incorporates dielectric screening to address the impact of shallow and deep traps.

A. Sreekanth Reddy, G. Nageswara Reddy

In this paper, an adaptive FO − IλD1−λ controller design is proposed using a frequency domain approach. The proposed adaptive controller parameters are tuned based on the frequency domain specifications. To realize the velocity error constant for the proposed controller, Oustaloup Recursive Approximation (ORA) method is employed. The proposed controller is realized for liquid level regulation in the Liquid Level Plant (LLP). An identification technique is proposed to identify a linear adaptable parameter transfer function (LAPTF) model of LLP. The performance of the proposed controller is compared with the existing works. It is observed that the proposed controller outperforms the existing controllers in the literature.

Shuxin Li, Wenxin Lin, Haonan Feng et al.

Abstract Although quantum dot light‐emitting diodes (QLEDs) are extensively studied nowadays, their charge transport mechanism remains a subject of ongoing debate. Here, the hole transport in blue quantum dots (QDs) (CdZnSe/ZnSe/ZnS/CdZnS/ZnS based) is investigated by combining current‐voltage and transient electroluminescence measurements. The study demonstrates that the hole transport in QD thin films is characterized by a trap‐free space‐charge‐limited current with a zero‐field room temperature mobility of 4.4 × 10−11 m2 V−1 s−1. The zero‐field hole mobility is thermally activated with an activation energy of 0.30 eV. Applying the Extended Gaussian Disorder model provides a consistent description of the QD hole current as a function of voltage and temperature. The QD hole mobility is characterized by a hopping distance of 2.8 nm in a Gaussian broadened density of states with a width of 0.12 eV.

Guoyi Xu, Edwin C. Kan

Phase measurements by the quadrature scheme in radio transceivers can be applied to phase-sensitive applications like precision multi-static 3D localization. However, measurements at different channels with individual local oscillators suffer from random phase offsets due to non-repeatable initial phases of phase-locked loops in frequency synthesizers. In this paper, a novel phase calibration method is proposed to cancel out both the random and systematic time-invariant phase offsets at the superheterodyne receiver frontends. Direct phase offset measurements and on-site calibration are made possible by additional hardware connections, achieving simple implementation and accurate differential phase measurements without relying on bandwidth resources. The proposed calibration method generates repeatable phases for each device reboot with standard deviation less than 2 degrees, which translates to 0.9 mm ranging accuracy for 1.8 GHz carrier frequency. This method can also be flexibly extended to accommodate a broad range of practical network scenarios with more channels, various network topologies, and a wider bandwidth.

Bhagappa, H.S. Divyashree, N. Avinash et al.

Wireless Network is usually a non-infrastructure multi-hop network, in which the communication between the nodes are carried implicitly or explicitly with the help of intermediate nodes. The two primary considerations when creating a wireless network are energy efficiency and secrecy, which are currently hot topics in study. Power-related issues make the conventional tiered approach ineffective. We suggest a novel solution to address those problems: the Young's double slit experiment optimizer (YDEO) based optimized cross layer routing protocol. This method computes parameters like data success rate, average energy loads, and traffic indices to determine consistency and energy efficacious routing paths. The secrecy of the network can be enhanced with the proposed innovative approach known as Hybrid Elliptic Curve Cryptography and Diffie Hellman Key Exchange (HECC-DH). This greatly enhances data integrity and security by offering dual authentications with key exchange techniques. In addition to this HECC-DH, bilinear maps are used for secure communication. To verify the effectiveness of the suggested work, experiments are performed with the NS2 simulator and contrasted with state-of-the-art works. When it comes to communication, our method performs better than the others and with greater satisfaction.

Yaoyao Jin, Ming Zhu, Yuhong Zhou et al.

Abstract Apart from simulating biological synapses, memristors can also be used in the secure encryption by exploiting their inherent random resistive switching (RS) properties. In this work, nonvolatile Ta/BiFeO3/ZrO2/Pt memristor is fabricated with 2 nm inserting BiFeO3 layer. At a high compliance current of 10 mA, it presents gradual RS characteristics during the set process, which resulting in 30 conductance states. Synaptic behavior can be successfully mimicked by precise conductance modulating under pulse electrical stimulation. Whereas under a low compliance current of 500 µA, it exhibits abrupt RS behavior, and the set voltage ranged from 0.3–0.8 V, which can be effectively as an entropy source for true random number generator (TRNG). Due to its Shannon entropy of 300 bits is 0.99987, Hamming weights and intra‐Hamming distances tend to be 50%. Furthermore, the software simulation of encryption and decryption of cat image is achieved by combining the key generated by TRNG. The controllable electrical properties of the Ta/BiFeO3/ZrO2/Pt device can be modulated by the compliance current, thus meeting the computing or safety requirements, which provides a solid foundation for the development of integrating computation and security at the hardware level.

Galyna Sych, Patrice Rannou, Maxime Jullien‐Palletier et al.

Y. Alexanian, J. Saugnier, C. Decorse et al.

The possibilities of combining several degrees of freedom inside a unique material have recently been highlighted in their dynamics and proposed as information carriers in quantum devices where their cross-manipulation by external parameters such as electric and magnetic fields could enhance their functionalities. An emblematic example is that of electromagnons, spin-waves dressed with electric dipoles, that are fingerprints of multiferroics. Point-like objects have also been identified, which may take the form of excited quasiparticles. This is the case for magnetic monopoles, the exotic excitations of spin ices, that have been recently proposed to carry an electric dipole although experimental evidences remain elusive. Presently, we investigate the electrical signature of a classical spin ice and a related compound that supports quantum fluctuations. Our in-depth study clearly attributes magnetoelectricity to the correlated spin ice phase distinguishing it from extrinsic and single-ion effects. Our calculations show that the proposed model conferring magnetoelectricity to monopoles is not sufficient, calling for higher order contributions.

Qianbiao Liu, Xin Lin, Ariel Shaked et al.

Spin currents of perpendicularly polarized spins (z spins) by an in-plane charge current have received blooming interest for the potential in energy-efficient spin-orbit torque switching of perpendicular magnetization in the absence of a magnetic field. However, generation of z spins is limited mainly to magnetically or crystallographically low-symmetry single crystals (such as non-colinear antiferromagnets) that are hardly compatible with the integration to semiconductor circuits. Here, we report efficient generation of z spins in sputter-deposited polycrystalline heavy metal devices via a new mechanism of broken electric symmetries in both the transverse and perpendicular directions. Both the dampinglike and fieldlike spin-orbit torques of z spins can be tuned significantly by varying the degree of the electric asymmetries via the length, width, and thickness of devices as well as by varying the type of the heavy metals. We also show that the presence of z spins enables deterministic, nearly-full, external-magnetic-field-free switching of a uniform perpendicularly magnetized FeCoB layer, the core structure of magnetic tunnel junctions, with high coercivity at a low current density. These results establish the first universal, energy-efficient, integration-friendly approach to generate z-spin current by electric asymmetry design for dense and low-power spin-torque memory and computing technologies and will stimulate investigation of z-spin currents in various polycrystalline materials.

M. Lederer, A. Betzwar Kotas, G. Khatibi

Solder fatigue is among the predominant failure modes observed in power electronic modules. Under service conditions power electronic parts are exposed to repeated temperature swings originating from resistance heating. In consequence of a mismatch of the coefficients of thermal expansion, thermomechanical stresses are generated at material interconnects. Nevertheless, lifetimes of up to 30 years are requested for high reliability applications. Therefore, there is a demand for accelerated testing methods. However, due to strain rate dependence of inelastic deformations theoretical lifetime modeling is necessary to compare the results of accelerated test methods with usual service conditions. The present study reports on a mechanical testing method operating at the ultrasonic frequency of 20 kHz. During testing samples are exposed to repeated bending deformations until the solder joint finally breaks. The number of cycles to crack initiation is determined for different temperatures ranging from room temperature to 175 °C. Thereafter, an FEM computer simulation of the fatigue experiment is performed, where the visco-plastic Anand model serves as material model of the solder. The time to crack initiation in the solder is evaluated with a model of damage accumulation, which combines the Coffin-Manson model with a multiaxial version of the Goodman relation. It is demonstrated that this model can be applied to the solder alloys PbSnAg, Sn3.5Ag and SnSbAg.

Kalpana Rangra, Virender Kadyan, Monit Kapoor

Speech is an effective way for analyzing mental and psychological health of a speaker's. Automatic speech recognition has been efficiently investigated for human-computer interaction and understanding the emotional & psychological anatomy of human behavior. Emotions and personality are studied to have a strong link while analyzing the prosodic speech parameters. The work proposes a novel personality and emotion classification model using PSO (particle swarm optimization) based CNN (convolution neural network): (NPSO) that predicts both (emotion and personality) The model is computationally efficient and outperforms language models. Cepstral speech features MFCC (mel frequency cepstral constants) is used to predict emotions with 90% testing accuracy and personality with 91% accuracy on SAVEE(Surrey Audio-Visual Expressed Emotion) individually. The correlation between emotion and personality is identified in the work. The experiment uses the four corpora SAVEE, RAVDESS (Ryerson Audio-Visual Database of Emotional Speech and Song), CREMAD (Crowd-sourced Emotional Multimodal Actors Dataset, TESS (Toronto emotional speech set) corpus, and the big five personality model for finding associations among emotions and personality traits. Experimental results show that the classification accuracy scores for combined datasets are 74% for emotions and 89% for Personality classifications. The proposed model works on seven emotions and five classes of personality. Results prove that MFCC is enough effective in characterizing and recognizing emotions and personality simultaneously.

Jason Ostanek, Mohammad Parhizi, Judith Jeevarajan

Numerical modeling of thermal runaway in Lithium-ion batteries has become a critical tool for designing safer battery systems. Significant progress has been made in developing kinetic mechanisms for decomposition reactions and including additional physics such as venting and combustion. However, the governing heat conduction equation and decomposition reaction equations become numerically stiff during thermal runaway, which limits the utility of thermal abuse models to low-dimensional formulations. The present work introduces a new solution strategy, which switches from the full, 3D transient heat conduction formulation to an adiabatic, 0D lumped body formulation only during the stiff portion of the simulation, i.e., only during thermal runaway. To test the new solver, a 3D thermal abuse model was configured to simulate an oven test of an 18650-format cell. The new solver was exercised for scenarios of varying degrees of stiffness, and the results were compared with a baseline solver using typical integration methods. For an extremely stiff scenario, computation speed was increased by a factor of 183x relative to the baseline solver, with little impact on solution accuracy, thus effectively alleviating the numerical stiffness issue. The new solution strategy addresses the poor scalability of high-dimensional models, such as 3D-CFD-based thermal abuse models, and improves their practicality for industrial use.

Kwangro Lee, Tien Dat Ngo, Sungwon Lee et al.

Abstract Recently, 2D materials have been intensively investigated for their novel nanoelectronic applications; among these materials, tungsten diselenide (WSe2) is attracting substantial research interest due to its high mobility, sizable bandgap, and ambipolar characteristics. However, Fermi‐level pinning (FLP) at the metal–semiconductor contact is a critical issue preventing further integration of WSe2 to complementary metal–oxide–semiconductor (CMOS) technology. In this study, a facile doping method of oxygen (O2) plasma treatment and an aging effect to overcome the FLP of WSe2 field‐effect transistors (FETs) are utilized. After aging, a reduction is observed in FLP on oxidized WSe2 FETs, along with a decrease in pinning factor (S) for holes from −0.06 to −0.36. Further, the field‐effect mobility of high‐ (Pd) and low‐ (In) work‐function contacted WSe2 devices indicates the presence of more improvement in high‐work‐function metal‐contacted p‐type WSe2 FETs, which further strengthens the Fermi level de‐pinning behavior attributed to the O2 plasma and aging processes. The existence of different tunneling behaviors of Pd and In devices also confirms the effect of O2 plasma doping into WSe2 FETs. Ultimately, this work demonstrates a simple and efficient method for achieving the de‐pinning of Fermi‐levels and modulating FLP of 2D FETs.

Gunther Gust, Alexander Schlüter, Stefan Feuerriegel et al.

With the global effort to reduce carbon emissions, clean technologies such as electric vehicles and heat pumps are increasingly introduced into electricity distribution networks. These technologies considerably increase electricity flows and can lead to more coincident electricity demand. In this paper, we analyze how such increases in demand coincidence impact future distribution network investments. For this purpose, we develop a novel model for designing electricity distribution networks, called the distribution network reconfiguration problem with line-specific demand coincidence (DNRP-LSDC). Our analysis is two-fold: (1) We apply our model to a large sample of real-world networks from a Swiss distribution network operator. We find that a high demand coincidence due to, for example, a large-scale uptake of electric vehicles, requires a substantial amount of new network line construction and increases average network cost by 84 % in comparison to the status quo. (2) We use a set of synthetic networks to isolate the effect of specific network characteristics. Here, we show that high coincidence has a more detrimental effect on large networks and on networks with low geographic consumer densities, as present in, e. g., rural areas. We also show that expansion measures are robust to variations in the cost parameters. Our results demonstrate the necessity of designing policies and operational protocols that reduce demand coincidence. Moreover, our findings show that operators of distribution networks must consider the demand coincidence of new electricity uses and adapt investment budgets accordingly. Here, our solution algorithms for the DNRP-LSDC problem can support operators of distribution networks in strategic and operational network design tasks.

Satoru Hayami

We theoretically investigate electronic orderings with the electric axial moment without breakings of both spatial inversion and time-reversal symmetries in the zigzag-chain system. Especially, we elucidate the role of the local odd-parity hybridization arising from locally noncentrosymmetric lattice structures based on symmetry and microscopic model analyses. We show that the odd-parity crystalline electric field gives rise to an effective cross-product coupling between the electric dipole and electric toroidal dipole, the latter of which corresponds to the electric axial moment. As a result, the staggered component of the electric axial moment is induced by applying an external electric field, while its uniform component is induced via the appearance of staggered electric dipole ordering. We also show that uniform electric quadrupole ordering accompanies uniform electric axial moment. Furthermore, we discuss transverse magnetization as a consequence of the orderings with the uniform electric axial moment. Our results extend the scope of materials exhibiting electric axial ordering to those with locally noncentrosymmetric lattice structures.

Hao-Tian Guo, San-Dong Guo, Yee Sin Ang

Two-dimensional (2D) half-metallic materials are highly desirable for nanoscale spintronic applications. Here, we propose a new mechanism that can achieve half-metallicity in 2D ferromagnetic (FM) material with two-layer magnetic atoms by electric field tuning. We use a concrete example of experimentally synthesized CrSBr monolayer to illustrate our proposal through the first-principle calculations. It is found that the half-metal can be achieved in CrSBr within appropriate electric field range, and the corresponding amplitude of electric field intensity is available in experiment. Janus monolayer $\mathrm{Cr_2S_2BrI}$ is constructed, which possesses built-in electric field due to broken horizontal mirror symmetry. However, $\mathrm{Cr_2S_2BrI}$ without and with applied external electric field is always a FM semiconductor. A possible memory device is also proposed based on CrSBr monolayer. Our works will stimulate the application of 2D FM CrSBr in future spintronic nanodevices.

Jochen Stiasny, Spyros Chatzivasileiadis

The simulation of power system dynamics poses a computationally expensive task. Considering the growing uncertainty of generation and demand patterns, thousands of scenarios need to be continuously assessed to ensure the safety of power systems. Physics-Informed Neural Networks (PINNs) have recently emerged as a promising solution for drastically accelerating computations of non-linear dynamical systems. This work investigates the applicability of these methods for power system dynamics, focusing on the dynamic response to load disturbances. Comparing the prediction of PINNs to the solution of conventional solvers, we find that PINNs can be 10 to 1000 times faster than conventional solvers. At the same time, we find them to be sufficiently accurate and numerically stable even for large time steps. To facilitate a deeper understanding, this paper also present a new regularisation of Neural Network (NN) training by introducing a gradient-based term in the loss function. The resulting NNs, which we call dtNNs, help us deliver a comprehensive analysis about the strengths and weaknesses of the NN based approaches, how incorporating knowledge of the underlying physics affects NN performance, and how this compares with conventional solvers for power system dynamics.

Valentin Totev, Vultchan Gueorgiev

Tri Multy Rizkilina, Nur Rohman Rosyid

Data traffic on a dense network is a threat to cybercrime and a high vulnerability for technology companies so that the challenges to prevent it will be more diverse. Adding a strengthening of the boundary wall or firewall and sorting data through packet filtering plus writing firewall rules to prevent malware and attacks from outside at the network device level is an alternative to protect the traffic you have. When heavy traffic makes data exchange uncontrollable, this research will create an automation design so that the sorting of incoming data packets through selection based on the specified rules runs in real-time so that the prevention of crime that enters the network is more swiftly handled. The system is running successfully by connecting the MQTT Collector as a subscriber that uses the python programming language to retrieve profiling data from the IP Profile database. The system was tested on a mikrotik router RB951Ui-2HnD which then the blocking track record will be stored in the Dynamic Firewall Data database in MongoDB. Also added a tool for controlling data in storage in the form of a program release. The results of the test show that data with an average base score above 20 is blocked and then stored in the block list in checking the collection in the database every 30 seconds. In addition, the data in the database will be checked every day within 30 days which will then be released and recorded in the release log in MongoDB.