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

Eglė Tankelevičiūtė, Sandra Jenatsch, Beat Ruhstaller et al.

Abstract The stability of organic light‐emitting diodes (OLEDs) is a key requirement for their use in commercial displays. One approach to increase the performance of the blue subpixel is to use thermally activated delayed fluorescence (TADF) emitters, which combine a small singlet‐triplet gap, ΔEST, and non‐trivial spin‐orbit coupling to enable the harvesting of both singlet and triplet excitons to produce light; however, device stability is compromised due to long triplet lifetimes that increase the probability of the degradation of materials by biexcitonic and polaron events. In this work, we correlate the efficiency and stability of the device with the device structure, identifying possible origins for the trade‐off between device efficiency and stability. By comparing a set of sky‐blue emissive devices and fitting drift‐diffusion simulations to intermittent optoelectronic measurements during stress‐testing, the layers most affected by degradation can be determined. By coupling electrical simulations to an excitonic model, the contributions from biexcitonic and polaronic events to efficiency roll‐off can be distinguished. We find that efficient but less stable devices suffer mainly from exciton‐exciton annihilation, while stable but less efficient devices have excitons predominantly quenched by polarons. This implies that the device structure is responsible for determining non‐radiative exciton pathways, and an efficient and stable OLED structure should aim to minimize exciton accumulation at high brightness.

Yuya Hirose, Naoya Kakutani, Fumiya Komatsu et al.

In this paper, K-band high-power rectification and its efficiency are discussed in theoretical and experimental approaches. A gated anode diodes (GAD) configured with a gallium arsenide (GaAs) enhancement-mode pseudomorphic high-electron-mobility-transistor (E-pHEMT) is focused as a rectifier diode. The GaAs E-pHEMT GAD is characterized to formulate its rectification efficiency. In K-band rectification at an input power of 100 mW or less, it is analytically clarified that the 0.18 μm GaAs E-pHEMT GAD, manufactured using a standard GaAs process, exhibited a rectification efficiency within 2% of that of the commercially available GaAs Schottky barrier diode (SBD) (MACOM MA4E1317) widely used in millimeter wave systems. For the K-band 1 W rectifier MMIC demonstrated in this paper, multi-stage series-connected GaAs E-pHEMT GADs with a wider gate width are used to achieve high-power rectification with high efficiency. For the prototyped K-band 1 W rectifier MMIC, the gate width and the stage number of the series-connected GADs are optimized and a rectification efficiency of 64% at 26.5 GHz is achieved. This is the highest value reported for 50 Ω matched watt-class rectifiers. The results confirm that the proposed design approach with the GaAs E-pHEMT GAD is effective for high-power rectification in the K-band.

Stephan Menzel, Benedikt Kersting, Rana Walied Ahmad et al.

Abstract In this work, a compact model for mushroom‐type phase‐change memory devices is introduced that incorporates the shape and size of the amorphous mark under different programming conditions, and is applicable to both projecting and non‐projecting devices. The model includes analytical equations for the amorphous and crystalline regions and uniquely features a current leakage path that injects current at the outer edge of the electrodes. The results demonstrate that accurately modeling the size and shape of the phase configurations is crucial for predicting the full‐span of the RESET and SET programming, including the characteristics of threshold switching. Additionally, the model effectively captures read‐out behaviors, including the dependence of resistance drift and bipolar current asymmetry behaviours on the phase configurations. The compact model is also provided in Verilog–A format, so it can be easily used in standard circuit‐level simulation tools.

Farzin Asadi

Peter Hayoung Chung, Jiyeon Ryu, Daejae Seo et al.

Abstract Artificial synapse devices are essential elements for highly energy‐efficient neuromorphic computing. They are implemented as crossbar array architecture, where highly selective synaptic weight updates for training and sneak leakage‐free inference operations are required. In this study, self‐selective bipolar artificial synapse device is proposed with n‐ZnO/p‐NiOx/n‐ZnO heterojunction, and its analog synapse operation with high selectivity is demonstrated in 32 × 32 crossbar array architecture without the aid of selector devices. The built‐in potential barrier at p‐NiOx/n‐ZnO junction and the Zener tunneling effect provided nonlinear current–voltage characteristics at both voltage polarities for self‐selecting function for synaptic potentiation and depression operations. Voltage‐driven redistribution of oxygen ions inside n–p–n oxide structure, evidenced by x‐ray photoelectron spectroscopy, modulated the distribution of oxygen vacancies in the layers and consequent conductance in an analog manner for the synaptic weight update operation. It demonstrates that the proposed n–p–n oxide device is a promising artificial synapse device implementing self‐selectivity and analog synaptic weight update in a crossbar array architecture for neuromorphic computing.

Itamar Melamed, Avraham Sayag, Emanuel Cohen

This paper presents a 28 GHz integrated phased-array transmitter, utilizing an over-the-air (OTA) combining technique for power efficiency boosting and a local oscillator (LO) phase shifting. Efficiency boosting is achieved by decomposing the baseband signal into two streams, one with a reduced peak-to-average power ratio (PAPR) and the other consisting of the low-occurrence peak residuals. Compared to uniformly excited linear phased array (UELA), the efficiency improvement is by 40<inline-formula><tex-math notation="LaTeX">$\%$</tex-math></inline-formula>. The two streams are up-converted and transmitted through the radio-frequency (RF) chains, each optimized for the corresponding output power, and recombined OTA to reconstruct the original signal. Each chain contains a power-optimized sub-sampling phase-locked loop (SSPLL) that accounts for the phase shift and achieves a better than 1<inline-formula><tex-math notation="LaTeX">$^\circ$</tex-math></inline-formula> phase resolution. We implemented the four TX chains on a standard 65 nm bulk-CMOS process, achieving a system efficiency of 7.6<inline-formula><tex-math notation="LaTeX">$\%$</tex-math></inline-formula> at 21 dBm equivalent isotropic radiated power (EIRP), with an error vector magnitude (EVM) of &#x2212;31 dB.

Lukas Pfromm, Alish Kanani, Harsh Sharma et al.

Due to reduced manufacturing yields, traditional monolithic chips cannot keep up with the compute, memory, and communication demands of data-intensive applications, such as rapidly growing deep neural network (DNN) models. Chiplet-based architectures offer a cost-effective and scalable solution by integrating smaller chiplets via a network-on-interposer (NoI). Fast and accurate simulation approaches are critical to unlocking this potential, but existing methods lack the required accuracy, speed, and flexibility. To address this need, this work presents CHIPSIM, a comprehensive co-simulation framework designed for parallel DNN execution on chiplet-based systems. CHIPSIM concurrently models computation and communication, accurately capturing network contention and pipelining effects that conventional simulators overlook. Furthermore, it profiles the chiplet and NoI power consumptions at microsecond granularity for precise transient thermal analysis. Extensive evaluations with homogeneous/heterogeneous chiplets and different NoI architectures demonstrate the framework&#x2019;s versatility, up to 340% accuracy improvement, and power/thermal analysis capability.

Wenjun Kuang, Xin Ma, Fanjiang Meng et al.

Alloy 690 exhibits much higher resistance to stress corrosion cracking (SCC) in pressurized water reactor (PWR) primary water than other engineering austenitic alloys as it is highly resistant to penetrative intergranular oxidation. Dynamic straining method can readily generate SCC initiation on Alloy 690 and increasing results indicate that there are some unique steps during the SCC initiation process of this alloy: the formation of protective oxide film above grain boundary and the subsequent fracture of such oxide film under dynamic straining. It was further revealed that local normal strain is the main driving force breaching the oxide film. Intergranular carbides further enhance the resistance to SCC initiation through: 1, decreasing the normal strain near grain boundary by impeding the movement of dislocations; 2, supplying additional Cr source for forming protective oxide when exposed to environment. Plastic deformation prior to or during SCC test can greatly weaken the mitigation effect of carbide and even reverse it. A certain amount of cold work and high tensile stress were shown to produce creep-induced cracking in the PWR operating temperature range due to the elevated density and enhanced diffusivity of vacancy. Moreover, although carbides diminish the local strain near grain boundary during dynamic straining, the dislocations accumulated near the matrix/carbide interface can expedite the ingress of oxygen once the surface oxide film is breached. There are still many critical research gaps that need to be filled in order to ensure the performance reliability of Alloy 690 during the lifespan of PWR.

Fan Ye, Amirhossein Hajiaghajani, Amir Zargari et al.

Abstract Current joint angle monitoring techniques—essential for evaluating biomechanical functions and rehabilitation outcomes—face significant challenges. These may include dependency on specific environmental lighting and clear line‐of‐sight, complex setup and calibration, or sensing modalities that may interfere with natural motion. Additionally, the durability of these methods is often compromised by mechanical failures due to repetitive motion. Here, textile (or skin‐borne) strongly coupled magnetic resonators that can be distributed cross‐body to form advanced joint monitoring networks is demonstrated. Flexible magneto‐inductive loops can be positioned adjacent to joints, continuously monitoring limb coordination without being directly subjected to large joint strains. Such a technique minimizes both impediments to joint motion and material fatigue. Networks are lastly utilized to monitor and identify limb activity during diverse user stretches and exercises.

Biswajit Bhattacharyya, Christian Balischewski, Jiyong Kim et al.

Abstract Transparent solid‐state ionic conductors are emerging as next‐generation materials for various modern optoelectronics and energy applications. In this study, an organic‐inorganic hybrid metal halide is introduced, tris‐N‐butyl pyridinium nonachlorido‐dibismuthate(III), (C4py)3[Bi2Cl9]. The material is an optically transparent solid‐state ion conductor with high ionic conductivity at room temperature. Single crystal analysis reveals a structure composed of N‐butyl pyridinium cations and [Bi2Cl9]3− anions, formed by edge‐sharing BiCl6 octahedra. The material is thermally stable up to 300 °C and undergoes a melting transition at 101.6 °C. Notably, it demonstrates unidirectional growth in thin films, boasting over 90% optical transparency in the visible wavelength and overall ionic conductivity of 10−3 mS cm−1 at room temperature. (C4py)3[Bi2Cl9] stands out as one of the first reported low‐melting, optically transparent ionic solids, showcasing superior ion conduction and holding promise for applications such as electrochromic devices and energy storage.

Xuan Zhao, Yi Wang, Pengfei Zhuang

We present a relativistic analysis of fermions in an external electric field by non-perturbatively solving the Dirac equation with a static gauge. Different from the magnetic field effect, the fermion wave function in an electric field oscillates asymptotically, which reflects the Klein paradox in the relativistic case and results in the absence of bound states in an infinite system. For a confined fermion, the confinement is gradually canceled by the electric field, and the fermion becomes deconfined when the electric coupling is stronger than the confinement coupling. However, a fermion in an electric field can be confined to a finite system by applying the MIT bag boundary condition, namely, the disappearing normal component of the probability current at the boundary. The result of this work can be applied to the physics of relativistic heavy ion collisions, where the strongest electric field in nature is expected to be created.

Mona Ghassemi

To achieve net-zero emissions by 2050, all-electric transportation is a promising option. In the U.S., the transportation sector contributes the largest share (29 percent) of greenhouse gas emissions. While electric vehicles are approaching maturity, aviation is only beginning to develop electrified aircraft for commercial flights. More than 75 percent of aviation emissions come from large aircraft, and this impact will worsen with 4-5 percent annual air travel growth. Aircraft electrification has led to two types: more electric aircraft (MEA) and all-electric aircraft (AEA). A MEA replaces subsystems such as hydraulics with electric alternatives, whereas an AEA uses electrically driven subsystems and provides thrust fully from electrochemical energy units (EEUs). For wide-body AEA, thrust demand is about 25 MW plus 1 MW for non-thrust loads, creating major challenges for electric power system (EPS) design. Achieving maximum power density requires minimizing mass and volume. Increasing voltage into the kilovolt range using medium-voltage direct current (MVDC) is a feasible option to enhance power transfer. Consequently, designing an MVDC EPS for wide-body AEA is critical. Because EPS failures could jeopardize passenger safety, reliability and resilience are essential. This chapter presents a load-flow model for DC systems to determine power flows in both normal and single-contingency conditions, followed by analysis of optimal MVDC EPS architectures. A complete EPS for wide-body AEA is introduced, with EEUs and non-propulsion loads located, distances estimated, and flow studies performed. Multiple architectures are evaluated for reliability, power density, power loss, and cost to identify optimal solutions.

Ambachew Bizuneh, Hunachew Mitiku, Ayodeji Olalekan Salau et al.

As industrial technology advances, there is an increasing need for very precise position control mechanisms for highly integrated and accurate products. Therefore, high precision positioning systems play an essential part in today's manufacturing processes. Piezoelectric actuators offer the requisite stiffness and positioning precision, but they have a limited traveling range. The combination of a linear motor with air bearings is a typical method for achieving long stroke movement at high speeds. However, to accomplish extensive and precise motion in several degrees of freedom with a linear motor and non-contact bearing, a sophisticated system setup is required. In this paper, a proportional-integral-derivative-proportional (PID-P) controller is presented for magnetic levitation system position control. Particle swarm optimization (PSO) and Black window optimization (BWO) algorithms are proposed for tuning the PID-P controller parameters. The PSO and BWO algorithms are employed by considering Integral Time Absolute Error (ITAE) as an objective function with rise-time and percentage peak overshoot as constraints. Furthermore, the performance of PSO and BWOA tuned PID-P controllers is compared to conventional PID-P and PID controllers using time response specifications such as rise time, settling time, and percentage peak overshoot. The graphical and numerical simulation results show that the PSO and BWOA tuned PID-P controller outperforms the conventional PID-P and PID controllers. The BWOA tuned PID-P controller outperformed the PSO tuned PID controller and the classical PID-P controller by 8.5 % in rise time, 46.77 % in settling time, and 86.6 % in percentage peak overshoot.

Zixin Ren, Bo Gao, Song Xu et al.

Abstract With humongous demand for data storage and processing, two‐dimensional (2D) ferromagnetic‐based materials, is emerged as the next‐generation nanoelectronic devices due to their low power consumption and optimal memory and processing capabilities. BiFeO3 as a single‐phase multiferromagnetic material is expected to find potential applications in electromagnetic devices. Herein, 2D room‐temperature ferromagnetic BiFeO3 is obtained with the help of supercritical carbon dioxide (SC CO2). The rhombic phase of BiFeO3 is converted to cubic with the creation of Ov and Fe2+ defects over the SC CO2 treatment, leading to significant ferromagnetic enhancement. More importantly, it is found that SC CO2 can destroy the cycloidal spin structure of BiFeO3 leading to an increase in the Fe─O─Fe bond angle, which generates stronger superexchange interactions. Ultimately, the saturation magnetization strength of BiFeO3 is increased by nearly 23 times. A new strategy is provided for ferromagnetic induction in 2D materials, which is favorable for promoting their practical applications on device architectures in the future.

Tong Fu, Qing Tong, Shiqi Jia et al.

Electric dark spots are point singularities at which the electric field amplitude vanishes. These singularities usually emerge in real space accidentally and are unstable due to the vectorial property of the electric field. In this paper, we show that topologically protected electric dark spots can emerge in metal scatterers under external excitation. The material property of metal imposes a boundary condition that reduces the vectorial electric field on the metal surface to a scalar field. The phase singularity of this scalar field has zero amplitude and carries a well-defined topological charge corresponding to an electric dark spot. The topological electric dark spots give rise to the superoscillation phenomenon with a divergent local wavenumber. We uncover the global charge conservation property of the dark spots on the scatterers' surfaces and demonstrate their stability under different perturbations. We also demonstrate the manipulation of the dark spots' topological charge and spatial location. The results open a new avenue for nanophotonic near-field manipulations and may find applications in optical metrology, optical sensing, and super-resolution imaging.

David Barranco, Şengül Kuru, Javier Negro

Electric and magnetic waveguides are considered in planar Dirac materials like graphene as well as their classical version for relativistic particles of zero mass and electric charge. In order to solve the Dirac-Weyl equation analytically, we have assumed the displacement symmetry of the system along a direction. In these conditions we have examined the rest of symmetries relevant each type, magnetic or electric system, which will determine their similarities and differences. We have worked out waveguides with square profile in detail to show up some of the most interesting features also in quantum and classical complementary contexts. All the results have been visualized along a series of representative graphics showing explicitly the main properties for both types of waveguides.

E. V. Chistyakova, D. N. Sidorov, A. V. Domyshev et al.

This paper describes a simplified model of an electric circuit with a DC-DC converter and a PID-regulator as a system of integral differential equations with an identically singular matrix multiplying the higher derivative of the desired vector-function. We use theoretical results on integral and differential equations and their systems to prove solvability of such a model and analyze its stability.

Teruo Matsushita

Sudeshna Baliarsingh, Prakash Kumar Panda, Mihir Narayan Mohanty

For a healthy society health of a human being needs to be taken care of. The smart age needs to provide adequate support to people in every respect. In this paper, authors have taken an approach to support e-healthcare systems in terms of cardiac signal compression that helps with data storage and communication. The compression method is performed using principal component analysis (PCA) that reduces the data redundancy. Initially, the Savitzky Golay filter (S Golay) is used for the pre-processing of the raw signals that follow the PCA application, further, the beta wavelet transform is put to use for thresholding purposes and to obtain exact information of the cardiac signal from the principal components. Finally, run-length encoding (RLE) is used that helps to communicate the data bits. The proposed method was found better, that comparison is demonstrated in the result section.

Kenneth K. O, Wooyeol Choi, Yukun Zhu et al.

Complementary Oxide Semiconductor (CMOS) integrated circuits (IC&#x2019;s) technology is emerging as a means for realization of capable and affordable systems that operate at frequencies near 300 GHz and higher. This is lowering a key barrier for utilizing the submillimeter electromagnetic waves in everyday applications. Despite the fact that the unity maximum available gain frequency, f max of <inline-formula> <tex-math notation="LaTeX">$N$ </tex-math></inline-formula>-channel MOS (nMOS) transistors (with connections to the top metal layer) has peaked at &#x007E;320 GHz, signal generation up to 1.33 THz, coherent detection up to 1.2 THz, and incoherent detection up to &#x007E;10 THz have been demonstrated using CMOS IC&#x2019;s. Furthermore, highly integrated rotational spectroscopy transceivers operating at frequencies up to near 300 GHz, and 400-GHz concurrent transceiver pixels and arrays for high-resolution radar imaging, and 300 and 390-GHz transmitters, and 300-GHz receivers for high data-rate communication have been demonstrated in CMOS. The performances of these CMOS circuits are sufficient or close to being sufficient to support electronic smelling using rotational spectroscopy that can detect and quantify concentrations of a wide variety of gases; imaging that can enable operation in a wide range of visually impaired conditions; and high-bandwidth communication. Finally, techniques for affordable packaging and testing submillimeter-wave systems are suggested based on experimental demonstrations.