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

Shilong Li, Linhai Li, Dehua Yang et al.

ABSTRACT Precise structural design and controllable fabrication of single‐wall carbon nanotube (SWCNT) heterojunctions are key to harnessing their optoelectronic performance and advancing high‐performance optoelectronic devices. Here, we integrated Rhodamine B (RhB) molecules into (6,5) SWCNT films via a simple immersion method, thereby forming a Type I heterojunction. A dual enhancement of photoluminescence (PL) and photoelectric conversion efficiency was experimentally observed for the first time in Type I heterojunction films, with external PL efficiency increasing by more than two‐fold and photoelectric conversion efficiency improving by approximately one order of magnitude. These enhancements are attributed to the strong π–π stacking interactions between RhB and (6,5) SWCNTs, as well as the favorable matching of their absorption bands, which facilitates efficient exciton energy transfer from RhB to SWCNTs and substantially increases exciton density in the (6,5) SWCNT films. Additionally, under illumination, the photoinduced electron transfer from RhB to SWCNTs results in the accumulation of positive charges within the RhB layer, triggering the photogating effect and further enhancing the photoconductivity gain. The findings provide new insights into exciton and electron transfer processes in Type‐I heterojunctions for enhancing the photoelectric performance of SWCNT films, offering guidance for the design of high‐performance photoelectric devices.

Aboudoul-Manaf Issifou, Smain Femmam, Selma Boumerdassi et al.

In Europe in general, and France in particular, building systems have evolved considerably over time, from the pre-war period to the industrialization era. Today's housing stock can be divided into 2 main categories: older buildings (built before 1948) and newer buildings built after 1948. The pre-1948 period is characterized by construction in phase with its environment, and can be subdivided into two main periods: before 1850 and between 1850-1948. Buildings constructed before 1850 were characterized by a wide disparity in construction methods, whereas buildings constructed between 1850 and 1948 were industrialized and saw a generalization of construction systems throughout France. These buildings are made of wood, earth, stone or timber, and were designed to be in total harmony with their immediate environment. They take many forms, such as Longères in the countryside, semidetached houses in historic villages, timber-framed houses, Haussmann-style collective buildings in major cities… One of the main characteristics of buildings constructed before 1948 is that they use local natural resources as raw materials. Wood, earth, brick and stone are always present, depending on the region. What's more, the heating system installed in these homes uses two energy sources to operate: wood and coal. Finally, the old building is a construction that has benefited from bioclimatic design, i.e. it has been designed in such a way that the immediate environment is taken into account to optimize its performance: the sunny facade has several openings to the outside and concentrates the living areas. The exterior is devoid of vegetation or buildings that could shade the building. The north-facing facade concentrates passageways such as outbuildings and stables. It has few openings to the outside, thicker walls and is protected by relief and/or lush vegetation. This bioclimatic design means that these homes consume very little energy. The vast majority of them are even rated D for energy efficiency, the average for French housing stock. After the Second World War came the “Trente Glorieuses” (1945-1975). This period of strong economic growth led to an acceleration in housing construction. Two types of housing sprang up all over France: “Habitations à Loyer Modéré” (HLM) and Favier-style suburban pavilions. During this period, the aim was to build quickly, even if this meant abandoning bioclimatic design. Industrial materials such as cement and oil were used, and housing did not benefit from bioclimatic design. As a result, the homes built at the time are considered to be thermal flats, most of them rated $F$ and $G$. 1974 saw the advent of new building regulations. After the first oil crisis, France discovers that it's no good being dependent on fossil fuels. So, France opted for nuclear power, and the French diversified their heating systems. Oil-fired systems gradually gave way to electric heating. It was at this time that the first “Réglementation Thermique” (RT) was introduced. The 1974 RT called for a diversification of construction methods and a focus on building insulation. This marked the advent of Positive Energy Buildings (BEPOS). The RT 1974 marks a turning point in French construction. For the first time, it regulated building design. Its main aim was to encourage individuals to insulate their homes through two types of work: roof insulation and wall insulation with brick lining and an air gap. This first Thermal Regulation was followed by several others, each presenting new work items to be integrated into housing design: the obligation to ventilate in the RT 1982; consideration of domestic hot water consumption in the RT 1988; calculation and limitation of the Primary Energy Consumption (PEC) of buildings for the RT 2000; limitation of PEC and consideration of summer overheating (TIC) for the RT 2005. RT 2012 introduces a new limit on RUE, a new design indicator (Bbio), a thermal study and an air-tightness test. And more recently, from 2022, the advent of the RE 2020 environmental regulation, which imposes 3 main additional objectives compared to RT 2012: to build “low-carbon” buildings over their entire life cycle; to further improve the energy performance of housing by further reducing energy consumption and increasing the production of renewable energy; to ensure occupant comfort during hot weather, while reducing cooling requirements as much as possible. As architectural systems have evolved, so have heating systems. What about underfloor heating? According to the study of remains, underfloor heating has existed since the 4th century B.C. However, this process was abandoned with the fall of the Roman Empire, only to reappear in the 1930s. But this underfloor heating technique was really developed in the 1960s. Water circulating in the floor was heated and transferred to the floor. The air mass in contact with the floor warmed up and rose until the room was heated by convection. Problems arose, however, with occupants experiencing headaches and leg pain, as the floor temperature was too high (over $30^{\circ}\mathrm{C}$). This technique was used for a few years, only to be abandoned again. Today, underfloor heating systems are referred to as “low temperature”. In fact, the temperature of the floor must not exceed 28° C (the average temperature of the arch of the foot). Water circulates in the floor, and the concrete slab stores and radiates energy. There's no accumulation of warm air, which avoids problems of discomfort. Underfloor heating systems can be adapted to all forms of energy production (solar, geothermal, oil, gas, electric, etc.), but particularly to environmentally-friendly heating systems such as geothermal and solar heating. In the 1930s, after the return of underfloor heating systems, some apartment buildings were equipped with hydraulic underfloor heating systems serving several apartments, i.e. one loop for several dwellings. Existing control systems on the market are unable to regulate these cases of buildings equipped with multi-zone loops. The aim of this article is to study possible technical solutions using artificial intelligence to control these types of circuits, thereby improving the energy efficiency of these buildings.

Josef Stevanus Matondang, Nikhilendu Tiwary, Glenn Ross et al.

Abstract Silicon‐on‐insulator (SOI) substrates suffer from heat‐confinement and self‐heating effects due to silicon dioxide's low thermal conductivity. Polycrystalline Aluminum nitride (AlN) films can be a good replacement for effective heat dissipation while being an excellent electrical insulator. This study reports AlN films grown using reactive magnetron sputtering, atomic layer deposition (ALD), and metalorganic vapour phase epitaxy (MOVPE) on Si (111) substrates. The strongly oriented MOVPE film has a thermal conductivity of 191 W m−1 K−1 and thermal boundary conductance (TBC) of 147 MW m−2 K−1. Modified Williamson‐Hall (W‐H) plot can provide grain size analysis for these highly oriented films to monitor the expected thermal conductivity. This study shows the feasibility of reactively sputtered and MOVPE AlN films as an integrated cross‐plane heat spreader in our AlN‐SOI platform.

David van Impelen, Lola González‐García, Tobias Kraus

Abstract A low‐temperature sintering mechanism of silver microparticles is established and used to enable the design‐for‐recycling of printed electronics. The formation of necks during the initial phase sintering of precipitated and atomized silver microparticles is studied. Temperature‐ and time‐dependent in‐situ analyses indicate the existence of a mobile silver species that provides efficient mass transport. The activation energy of neck formation identifies silver ion formation as the rate‐limiting step of low‐temperature silver sintering. It is demonstrated that resistivities of 271 times that of bulk silver can be attained after 40 minutes at 150°C. Low‐temperature sintering not only reduces the energy required during thermal treatment but it yields layers that are suitable for recycling, too. The resulting layers have conductive necks that are mechanically weak enough to be broken during recycling. Printed layers are redispersed and the recycled silver powder is reused without loss of the electrical performance in new prints. Their conductivities are industrially relevant, which makes this recyclability‐by‐design approach promising for manufacturing more sustainable printed electronics.

Jaanus Kalde, Veli-Pekka Kutinlahti, Anu Lehtovuori et al.

Traditional antenna array design aims at minimising the mutual coupling between the elements. When elements are fully isolated, the active impedance seen by the amplifiers does not depend on the beam steering angle. However, at the same time, the mutual coupling can not be exploited in re-configuring the operation of the antenna-amplifier system. In this paper, we show experimentally that increased mutual coupling between array elements can broaden the operation band of the system without any sacrifice in the efficiency or transmitted power. This severely challenges the traditional design paradigm and suggests that amplifiers and antennas should be co-designed.

Farzin Asadi

Preetinder Kaur, Mandeep Kaur, Bhavi Bhatia et al.

Partial discharges (PDs) often begin by electric insulation failure, which is the primary cause of apparatus breakdown in high-voltage networks. Electromagnetic interference, low sensitivity, and lack of spatial accuracy are among of the issues with conventional electrical PD detection techniques. This study uses spectroscopic measurement of light released during partial discharges to present an optical emission-based monitoring method. The research investigates the deployment of photodetectors and optical materials to record and examine the UV and visible light patterns linked to PD occurrences in the cable joints and air-insulated switchgear. As a non-invasive and EMI-immune diagnostic instrument, emission spectra related to insulation health and discharge intensity. Spectral decomposition and discharge dynamics visualization are achieved by the development of simulation models based on MATLAB. A controlled high-voltage setup with optical sensors and spectrometers is used for experimental validation. This method allows for early defect detection in high voltage electrical systems without physical contact, which increases safety and predictive maintenance capabilities.

Chenhao Zhang, Yazhe Niu

Metaphorical comprehension in images remains a critical challenge for AI systems, as existing models struggle to grasp the nuanced cultural, emotional, and contextual implications embedded in visual content. While multimodal large language models (MLLMs) excel in general Visual Question Answer (VQA) tasks, they struggle with a fundamental limitation on image implication tasks: contextual gaps that obscure the relationships between different visual elements and their abstract meanings. Inspired by the human cognitive process, we propose Let Androids Dream (LAD), a novel framework for image implication understanding and reasoning. LAD addresses contextual missing through the three-stage framework: (1) Perception: converting visual information into rich and multi-level textual representations, (2) Search: iteratively searching and integrating cross-domain knowledge to resolve ambiguity, and (3) Reasoning: generating context-alignment image implication via explicit reasoning. Our framework with the lightweight GPT-4o-mini model achieves SOTA performance compared to 15+ MLLMs on English image implication benchmark and a huge improvement on Chinese benchmark, performing comparable with the Gemini-3.0-pro model on Multiple-Choice Question (MCQ) and outperforms the GPT-4o model 36.7% on Open-Style Question (OSQ). Generalization experiments also show that our framework can effectively benefit general VQA and visual reasoning tasks. Additionally, our work provides new insights into how AI can more effectively interpret image implications, advancing the field of vision-language reasoning and human-AI interaction. Our project is publicly available at https://github.com/MING-ZCH/Let-Androids-Dream-of-Electric-Sheep.

Wenjie Zhang, Yuting Yang, Xiaopeng Shen et al.

Non-Hermitian topological insulators have attracted considerable attention due to their distinctive energy band characteristics and promising applications. Here, we systematically investigate non-Hermitian Möbius insulators and graphene-like topological semimetals from the projected symmetry and realize their corresponding topological phenomena in an electric circuit-based framework. By introducing a nonreciprocal hopping term consisting of negative impedance converters into a two-dimensional electric circuit, we establish an experimental platform that effectively demonstrates that introducing non-Hermitian terms significantly enhances the energy localization of topological edge states, which originate from the non-Hermitian skin effect. Furthermore, a thorough comparison of experimental measurements with numerical simulations validates the robustness and reliability of our electric circuit structure. This work not only reveals the physical properties of non-Hermitian topological materials but also provides valuable theoretical and experimental guidance for the implementation of topological circuits and the design of radiofrequency devices in the future.

V. Thulasi, P. Lakshmi, A. Sahithya

Abstract The power requirement of Smart Building-Wireless Sensor Network (SB-WSN) is achieved using the piezoelectric energy harvester. This article proposes a novel high-performance bimorph W-shaped Piezoelectric Energy Harvester (W-PEH) using different ceramic piezoelectric materials and proof mass material combinations [PZT-5A & Copper, PZT-5H & Copper, PZT-5J & Copper, PZT-5A & Platinum, PZT-5H & Platinum and PZT-5J & Platinum]. Three cases of W-PEH without proof mass, with single proof mass and with split proof mass are developed to improve the output performance. The electrical performance results under open and short circuit conditions are examined. The simulation is performed using COMSOL Multiphysics software.

Nicholas Krause, Dominick Sossong, Ian P. Brown

The parameters of electric machine thermal equivalent circuit networks are difficult to predict due to material and manufacturing uncertainties. In this paper, a Greybox system identification approach is used to identify parameters of electric machine stator lumped parameter thermal networks (LPTNs). LPTNs provide a low order, computationally efficient, dynamic model of temperatures at specific locations. Second and third order LPTN model structures are defined as state space equations with stator thermal parameters to be identified. To test the Greybox electric machine stator thermal system identification, five stator motorette prototypes were constructed with controlled variations in slot fill and slot liner thickness. The variation in the motorette thermal parameters and thermal time constants are detected using the Greybox identification. Special attention is given to the impact of sampling rate and Greybox data record length on parameter estimation accuracy.

Lianbin Xia, Hao Zhou, Jinkai Chen et al.

Abstract Triboelectric nanogenerator (TENG) is a promising technology, which can convert biokinetic energy into electricity and be utilized as self‐powered sensors and power sources for wearable electronics. The existing designs of conventional TENGs require complex fabrication processes and device structures, and they need to be attached on human body for wearable application, which is uncomfortable and may lead to malfunction under intense body moment. Here, a direct current TENG is proposed by utilizing natural human body, basketball, shoes, and ground floor. A unidirectional peak voltage and current output up to 700 V and 23 µA can be generated when a player plays a basketball, which can lighten up an array of 240 LEDs, and charge a 100 µF capacitor to 3.2 V in 1 min. The output of TENG is utilized to identify different movements of a basketball player using machine learning algorithm with an accuracy up to 96.7%. Moreover, the human body enabled direct current TENG (HBDC‐TENG) is used as a self‐powered sensor and an energy harvester for a wireless sensing system, which can collect human motion and environmental information, and transmit them wirelessly. The HBDC‐TENG has a great significance for self‐powered wearable electronics, providing a viable solution for human motion status and ambient environment monitoring.

Yunwoo Shin, Jaemin Son, Juhee Jeon et al.

Abstract In this study, a triple‐gated transistor with a p+‐i‐n+ silicon nanosheet (NS) is proposed as a single synaptic device, and bidirectional synaptic functions are realized using reconfigurable memory characteristics. The triple‐gated NS transistor features steep switching and bistable characteristics with a subthreshold swing below 5 mV dec−1 and an ON/OFF current ratio of ≈5 × 106 for both the n‐ and p‐channel modes. This transistor exhibits electrically symmetric reconfigurable memory characteristics with an ON current ratio of 1.02 for the n‐ and p‐channel modes. Moreover, the bidirectional synaptic weight updates of binarized spike‐timing‐dependent plasticity learning are successfully performed in a single transistor. This study demonstrates the potential of a triple‐gated NS transistor for achieving compact synaptic arrays in large‐scale silicon‐based neuromorphic computing systems.

Kamel BELKACEM, Noureddine BALI, Hilal LABDELAOUI

This work presents a comparative study of different meta-heuristic algorithms which are commonly used in the literature, such as Genetic Algorithms, Particle Swarm Optimization, Artificial Bee Colony and Grey Wolf Optimizer. These algorithms are applied to solve a multi-state system maintenance optimization problem considering time and system availability constraints. The objective is to find the optimal inspection and maintenance intervals for each component of the system in order to minimize the preventive maintenance cost of overall the system. The performances of the algorithms are compared using different metrics, regarding the quality and stability of the results and the speed of convergence, in order to determine the most efficient algorithms.

Lekai Song, Pengyu Liu, Jingfang Pei et al.

Abstract Implementing and integrating spiking neurons for neuromorphic hardware realization conforming to spiking neural networks holds great promise in enabling efficient learning and decision‐making. The spiking neurons, however, may lack the spiking dynamics to encode the dynamical information in complex real‐world problems. Herein, using filamentary memristors from solution‐processed hexagonal boron nitride, this study assembles leaky integrate‐and‐fire spiking neurons and, particularly, harnesses the common switching stochasticity feature in the memristors to allow key neural dynamics, including Poisson‐like spiking and adaptation. The neurons, with the dynamics fitted via hardware‐algorithm codesign, suggest a potential in realizing spike‐based neuromorphic hardware capable of handling complex problems. Simulation of an autoencoder for anomaly detection of time‐series real analog and digital data from physical systems is demonstrated, underscoring its promising prospect in applications, especially, at the edges with limited computation resources, for instance, auto‐pilot, manufacturing, wearables, and Internet of things.

Rami BOUMEGOURA, Riad BENDIB, Kamel MENIGHED

This paper investigates the control of a Continuous Stirred Tank Reactor (CSTR), with a primary emphasis on achieving temperature stability and optimizing reactant conversion. The CSTR poses challenges due to its nonlinear and exothermic behavior. To address these challenges, Model Predictive Control (MPC) is employed, a powerful strategy for handling complex systems. Additionally, Particle Swarm Optimization (PSO) is introduced to fine-tune MPC parameters, ensuring optimal performance. By integrating PSO with MPC, this study enhances control capabilities, specifically targeting the intricate demands of CSTR systems.

Zhikuan Wang, Ge Xu, Xinxin Jiang et al.

Abstract Searching for multiferroic materials with ferromagnetic (FM) and ferroelectric (FE) properties holds promise for ultra‐high‐density and low‐energy‐consumption memory device applications, but 2D materials with both properties are rare. Herein, a general strategy to achieve nonvolatile electric field control of magnetism in the bilayer (BL) α‐In2Se3 by hole doping is proposed. By first‐principles calculations, it is demonstrated that hole doping can induce robust ferromagnetism in the bilayer α‐In2Se3 due to its unique flat Mexican‐hat‐shape valence band structure. Such band edges cause van Hove singularities (VHS), and proper hole doping can lead to time‐reversal symmetry breaking. The bilayer α‐In2Se3 exhibits ferromagnetism and ferroelectricity within a wide range of doping concentrations, resulting in an unexpected multiferroic phase. Furthermore, when the electrical polarization of α‐In2Se3 flips from downward to upward, it becomes non‐magnetic (NM) from ferromagnetic states in the As‐substituted bilayer α‐In2Se3, which can work as a nonvolatile magnetic storage unit. Remarkably, the As‐substituted bilayer α‐In2Se3 exhibits an enhanced magnetic moment of 1.2 μB per AsSe due to substantial charge transfer across the interface. Notably, the mechanism of electrically controlled magnetism is elucidated as the coupling among the Mexican‐hat‐like dispersion, ferromagnetism, and ferroelectricity. The findings offer a promising strategy for electrical writing and the magnetic reading memory device.

A. Lansberg, A. V. Vinogradov

The relevance of the study lies in the consideration and correction of the results of calculations of the single-phase short circuit current in a rural 0.4 kV electric network obtained using existing physical, computer and mathematical methods that give different results. Purpose. Development of correction coefficients for different methods of calculating the single-phase short circuit current in a rural 0.4 kV electrical network. Materials and research methods. During the calculations of the single-phase short circuit current in the 0.4 kV rural electric grid, using different methods, general initial conditions were set: power was supplied from a TM-250 transformer and using A-35 wire. Results. It was revealed that the error between the results obtained using different methods reaches 35.9%. In the work, correction coefficients with values from 0.93 to 1.47 relative units were proposed in order to increase the reliability of calculations. These coefficients made it possible to increase the reliability of the considered methods for determining the current of a single-phase short circuit in a rural 0.4 kV electrical network by 2.9-6.1 times compared with the initial values.

D. Budáč, Vojtěch Miloš, M. Carda et al.

Solid oxide cells (SOCs) show high potential in energy conversion applications necessary for the decarbonization of the economy. Their advantage consists in ability to operate at high temperatures, reaching up to 900 °C. Firstly, it results in accelerated electrode reactions kinetics, secondly, in favorable thermodynamic conditions decreasing the equilibrium voltage of the water splitting. As a result, SOCs are attractive candidates for both efficient electrolysis and fuel cell applications, offering a robust solution in the pursuit of clean energy. However, the elevated operational temperature also introduces material challenges that hinder the competitiveness of SOCs. Porous gas diffusion electrodes are used to accomplish the desired electrode reactions. Considering conventional exclusively electron-conductive electrode materials, triple phase boundary (TPB) is required for the reactions to take place – a simultaneous contact of electron-conductive, ion-conductive and gaseous phase. While the electrode and electrolyte phases are solid, the gaseous phase is represented by open porosity in the electrode body. TPB is located exclusively at the contact area of electrode and electrolyte components in the case of single-phase electrodes, limiting the electrode electrocatalytic performance. To avoid the limitation by TPB length, composite electrodes are frequently used. Due to the involvement of the ionically conductive phase, they exhibit improved electrocatalytic capabilities. Electrolyte phase, however, usually exhibits 4 orders of magnitude lower electrical conductivity than the electron-conductive phase, while gaseous phase is electrically non-conductive. Thus, an improper phase composition and morphology of the composites can lead to a significant drop in their electrical conductivity and thus in the cell performance. Simple and reliable method for the conductivity value prediction is up to now missing. At the same time, experimental determination is both expensive and time-consuming. The goal of this study was to develop simple, fast and reliable method for prediction of electrical conductivity of the porous electron-ion conductor composites. The key feature of the presented approach lies in the minimal requirements for input parameters. Only electrode phase composition and bulk electrical conductivity of each phase are required. Based on the input composition, the model generates a 3D artificial specimen, a domain discretized into cubic voxels each assigned randomly to a specific phase. The resulting structure is substituted with an equivalent circuit network with electric elements corresponding to the electrochemical properties of the material components: specific resistivity of electrical conductors and polarization resistance / capacitance of electrochemical reaction at material interface. In-silica electrochemical impedance spectroscopy measurement is performed by solving charge balance following Kirchhoff’s current law for multiple frequency values. Resulting impedance spectrum is fitted in order to obtain Ohmic and polarization resistance and the capacitance of the artificial specimen. This procedure is averaged over a large number of artificial specimens in a Monte Carlo manner. Conventionally used oxygen electrode composite material lanthanum strontium manganite (LSM) mixed with yttria-stabilized zirconia (YSZ) was used to produce validation dataset. LSM:YSZ powder mixtures of compositions between 1:0 and 0:1, chosen to produce samples of various degree of LSM percolation, were homogenized. The mixtures were fired at 1150 °C. Electrical conductivity of the pellets was determined at temperatures between 600 and 800 °C using electrochemical impedance spectroscopy. Experimental data obtained were confronted to the model results. The model demonstrated very good accuracy for a porosity value of up to 55%. Significant error was observed in the porosity range between 55% and 68%. Finally, the model failed to generate an artificial specimen with a porosity of 75%. As it was found, the limited applicability of the model for the materials characteristic for high porosity was caused by the coalescence of the void phase. This shortcoming of the model was solved by implementing morphological parameter describing degree of void phase coalescence in the electrode structure. Due to this modification, model allows to gain valuable information on the microstructure of the studied composite material on the base of the experimentally determined conductivity data. This work introduces a novel modelling approach with minimal amount of input parameters, streamlining the prediction of electrical conductivity of porous electron-ion conductor composites. This simplified yet effective methodology holds great promise for efficiently characterizing and optimizing materials for energy conversion applications, offering a valuable tool for advancing research in the field. This publication was supported by the project "The Energy Conversion and Storage", funded as project No. CZ.02.01.01/00/22_008/0004617 by Programme Johannes Amos Commenius, call Excellent Research.