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Dielectric Strength of Transformer Oil of Various Qualities

Journal of engineering Science and Technology Review 2021年第1期14卷 201-205页

作者： Rallis, G. Sarathi, R. Danikas, G. Democritus University of Thrace Department of Electrical and Computer Engineering Electric Power Systems Laboratory Xanthi67100 Greece Indian Institute of Technology Madras Department of Electrical Engineering Chennai India

This paper focuses on the effects of dielectric strength on transformer oil reliability and on a reproduction of a voltage breakdown simulation during a dielectric strength test. A typical Foster test cell was used in order to measure the dielectric strength of a variety of oils. For a more complete picture, it requires the identification of more parameters but this paper examines only the above one as a result of the operation of a testing apparatus. It is shown that FEM/FDM analysis provides same information for the electrode gap. Bruce electrode provides highly uniform electric field. Factors such as voltage rate, relaxation time between measurements as well as the shape of the testing electrodes influences the dielectric strength of the liquid. © 2021 School of Science, IHU. All rights reserved.

关键词： Electrodes

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A Study of Two Types of Introductory Exercise Problems for Network Programming Learning with Python 23

A Study of Two Types of Introductory Exercise Problems for N...

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11th International Conference on computer and Communications Management, ICCCM 2023

作者： Lu, Xiqin Funabiki, Nobuo Ueda, Kiyoshi Kao, Wen-Chung Department of Information and Communication Systems Distributed System Design Lab. Okayama University Okayama Japan Department of Computer Science Control Software Lab. Nihon University Koriyama Japan Department of Electrical Engineering National Taiwan Normal University Taipei Taiwan

ISBN: (纸本)9798400707735

Network programming is the act of writing computer codes for communications between programs or processes in different computers across networks. It is crucial for applications and services using networks, including e-commerce, gaming, and social media. However, university courses of educating it are very limited. As a result, it has become important to develop and offer IT tools to support self-studies of network programming by novices. In this paper, we present a study of two types of introductory exercise problems, namely, Grammar-concept Understanding Problem (GUP) and Comment Insertion Problem (CIP), for self-studies of five basic network protocols of TCP/IP, ARP, SMTP, POP3, and SSH with Python. A GUP instance requests to answer the keyword such as a library function in the given source code that corresponds to the grammar concept described in the question. A CIP instance requests to insert the comment at each blank of the code. String matching is adopted to mark any answer at the browser-based answer interface. Through solving them, it is expected to understand the meaning of important words and the code structure for network programming. As preliminary evaluations, we generated six GUP and CIP instances respectively, and assigned them to 10 students in Okayama University, Japan. The results confirmed that the proposal is proper for novices to learn network programming with Python. © 2023 ACM.

关键词： Python

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A Tube-Based Reinforcement Learning Approach for Optimal Motion Planning in Unknown Workspaces

A Tube-Based Reinforcement Learning Approach for Optimal Mot...

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IEEE International Conference on Robotics and Automation (ICRA)

作者： Panagiotis Rousseas Charalampos P. Bechlioulis Kostas J. Kyriakopoulos School of Mechanical Engineering Control Systems Laboratory National Technical University of Athens Greece Department of Electrical and Computer Engineering University of Patras

ISBN: (数字)9798350384574

ISBN: (纸本)9798350384581

In this work, a tube-based nearly optimal solution to motion planning in unknown workspaces is presented. The advantages of reactive motion planning are combined with a Policy Iteration Reinforcement Learning scheme to yield a novel solution for unknown workspaces that inherits provable safety, convergence and optimality. Moreover, in simply-connected workspaces, our method is proven to asymptotically provide the globally optimal path. Our method is compared against a provably asymptotically optimal RRT ⋆ method, as well as a relevant reactive method and provides satisfactory performance, closely matching or outperforming the former.

关键词： Reinforcement learning Planning Safety Robotics and automation Convergence

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MMAL: Multi-Modal Analytic Learning for Exemplar-Free Audio-Visual Class Incremental Tasks 24

MMAL: Multi-Modal Analytic Learning for Exemplar-Free Audio-...

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32nd ACM International Conference on Multimedia, MM 2024

作者： Yue, Xianghu Zhang, Xueyi Chen, Yiming Zhang, Chengwei Lao, Mingrui Zhuang, Huiping Qian, Xinyuan Li, Haizhou Department of Electrical and Computer and Engineering National University of Singapore Singapore Laboratory for Big Data and Decision National University of Defense Technology Hunan Changsha China School of Electronic Electrical and Communication Engineering University of the Chinese Academy of Sciences Beijing China National Key Laboratory of Information Systems Engineering National University of Defense Technology Hunan Changsha China Shien-Ming Wu School of Intelligent Engineering South China University of Technology Guangdong Guangzhou China School of Computer and Communication Engineering University of Science and Technology Beijing Beijing China Shenzhen China

ISBN: (纸本)9798400706868

Class-incremental learning poses a significant challenge under an exemplar-free constraint, leading to catastrophic forgetting and sub-par incremental accuracy. Previous attempts have focused primarily on single-modality tasks, such as image classification or audio event classification. However, in the context of Audio-Visual Class-Incremental Learning (AVCIL), the effective integration and utilization of heterogeneous modalities, with their complementary and enhancing characteristics, remains largely unexplored. To bridge this gap, we propose the Multi-Modal Analytic Learning (MMAL) framework, an exemplar-free solution for AVCIL that employs a closed-form, linear approach. To be specific, MMAL introduces a modality fusion module that re-formulates the AVCIL problem through a Recursive Least-Square (RLS) perspective. Complementing this, a Modality-Specific Knowledge Compensation (MSKC) module is designed to further alleviate the under-fitting limitation intrinsic to analytic learning by harnessing individual knowledge from audio and visual modality in tandem. Comprehensive experimental comparisons with existing methods show that our proposed MMAL demonstrates superior performance with the accuracy of 76.71%, 78.98%, and 76.19% on AVE, Kinetics-Sounds, and VGGSounds100 datasets, respectively, setting new state-of-the-art AVCIL performance. Notably, compared to those memory-based methods, our MMAL, being an exemplar-free approach, provides good data privacy and can better leverage multi-modal information for improved incremental accuracy. © 2024 ACM.

关键词： Contrastive Learning

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Robust Control of Feeding Speed in Coal Seam Drilling Process Considering Borehole Friction

Robust Control of Feeding Speed in Coal Seam Drilling Proces...

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2024 China Automation Congress, CAC 2024

作者： Liu, Xiao Chen, Luefeng Lu, Chengda Fan, Haipeng Wu, Min Pedrycz, Witold School of Automation The Hubei Key Laboratory of Advanced Control and Intelligent Automation for Complex Systems The Engineering Research Center of Intelligent Technology for Geo-Exploration Ministry of Education China University of Geosciences Wuhan430074 China Department of Electrical and Computer Engineering University of Alberta EdmontonABT6G 2R3 Canada Systems Research Institute Polish Academy of Sciences Warsaw00-901 Poland Department of Computer Engineering Istinye University Sariyer Istanbul34396 Turkey

ISBN: (纸本)9798350368604

During the coal seam drilling process, the drill string is subject to compressive deformation, compounded by unpredictable variations in formation hardness and borehole wall friction, leading to challenges in maintaining a stable feeding speed. This paper presents a novel approach by introducing uncertain parameters to describe the effects of formation hardness and borehole wall friction. Drill string axial movement model is modeled as a polyhedral system based on a lumped parameter representation. To meet industrial performance requirements, we design a robust H∞ controller to achieve consistent feeding speed control. Our simulation results demonstrate the controller’s effectiveness in ensuring system stability despite fluctuations in formation hardness and drill string friction. © 2024 IEEE.

关键词： Coal deposits

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Van der Waals integration inch-scale 2D MoSe_(2) layers on Si for highly-sensitive broadband photodetection and imaging

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Nano Research 2023年第8期16卷 11422-11429页

作者： Yupiao Wu Shuo-En Wu Jinjin Hei Longhui Zeng Pei Lin Zhifeng Shi Qingming Chen Xinjian Li Xuechao Yu Di Wu School of Physics and Microelectronics and Key Laboratory of Material PhysicsZhengzhou UniversityZhengzhou 450052China Department of Electrical and Computer Engineering University of California San DiegoLa JollaCA 92093USA School of Microelectronics Science and Technology Sun Yat-Sen UniversityZhuhai 519082China Key Laboratory of Multifunctional Nanomaterials and Smart Systems Suzhou Institute of Nano-Tech and Nano-BionicsChinese Academy of SciencesSuzhou 215123China

As one of the most promising materials for two-dimensional transition metal chalcogenides(2D TMDs),molybdenum diselenide(MoSe_(2))has great potential in photodetectors due to its excellent properties like tunable bandgap,high carrier mobility,and excellent air *** 2D MoSe_(2)-based photodetectors have been reported to exhibit admired performance,the large-area 2D MoSe_(2)layers are difficult to be achieved via conventional synthesis methods,which severely impedes its future ***,we present the controllable growth of large-area 2D MoSe_(2)layers over 3.5-inch with excellent homogeneity by a simple post-selenization ***,a high-quality n-MoSe_(2)/p-Si van der Waals(vdW)heterojunction device is in-situ fabricated by directly growing 2D n-MoSe_(2)layers on the patterned p-Si substrate,which shows a self-driven broadband photoresponse ranging from ultraviolet to mid-wave infrared with an impressive responsivity of 720.5 mA·W^(−1),a high specific detectivity of 10^(13) Jones,and a fast response time to follow nanosecond pulsed optical *** addition,thanks to the inch-level 2D MoSe_(2)layers,a 4×4 integrated heterojunction device array is achieved,which has demonstrated good uniformity and satisfying imaging *** large-area 2D MoSe_(2)layer and its heterojunction device array have great promise for high-performance photodetection and imaging applications in integrated optoelectronic systems.

关键词： molybdenum diselenide large-area synthesis broadband photodetector integrated device array van der Waals(vdW)heterojunction

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Analysis of Partial Discharge Characteristics of MVDC Power Cables Optimally designed for All-Electric Wide Body Aircraft Under Varying Pressure During Takeoff and Descent

Analysis of Partial Discharge Characteristics of MVDC Power ...

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Conference on electrical Insulation and Dielectric Phenomena, (CEIDP)

作者： Md Asifur Rahman Anoy Saha Saikat Chowdhury Mona Ghassemi Jane Lehr Department of Electrical and Computer Engineering Zero Emission Realization of Optimized Energy Systems (ZEROES) Laboratory The University of Texas at Dallas Richardson TX USA Department of Electrical and Computer Engineering University of New Mexico Albuquerque UM USA

ISBN: (数字)9798350366679

ISBN: (纸本)9798350366686

Introducing all-electric aircraft (AEA) is a viable option to reduce greenhouse gas (GHG) emissions from the aviation sector. The wide-body AEA's electric power system needs higher voltage levels (a few kVs) than the voltage levels of existing aircraft cables. Consequently, the aircraft cable insulation needs to withstand higher voltage, maintaining low mass since the EPS contributes about 30% of the total mass of aircraft. Aircraft cables face several challenges: arcing, partial discharge (PD), and electromagnetic interference due to low-pressure environments at high altitudes. Several multilayer insulation designs for aircraft cables were proposed to overcome these challenges, and the optimized fabrication process of these cables was presented in our previous works. This paper analyzes the PD characteristics of fabricated flat insulation samples for the cables under different air pressures as the aircraft operates from 1 atm at the time of takeoff to 18.8 kPa at the typical cruising altitude (12.2 km).

关键词： Partial discharges Insulation Power cables Voltage Nonhomogeneous media Power systems Aircraft Greenhouse gases Faces Cables

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An Optimal Approach to Fabricate MVDC Multilayer Insulation systems as Flat Samples for Wide-Body All-Electric Aircraft

An Optimal Approach to Fabricate MVDC Multilayer Insulation ...

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Proceedings of the IEEE Dallas Circuits and systems Workshop (DCAS)

作者： Saikat Chowdhury Arian Azizi Anoy Saha Md Asifur Rahman Mona Ghassemi Jane Lehr Department of Electrical and Computer Engineering Zero Emission Realization of Optimized Energy Systems (ZEROES) Laboratory The University of Texas at Dallas Richardson TX USA Department of Electrical and Computer Engineering University of New Mexico Albuquerque UM USA

ISBN: (数字)9798350349535

ISBN: (纸本)9798350349542

To accomplish the net zero emission target, the current fuel-based transportation sector, which is the largest greenhouse gas emitter, needs to be decarbonized. Moving towards electrified ones is a highly promising solution to reduce carbon emissions. Aviation sectors, which rely on fossil fuels and emit harmful pollutants, are also being challenged by electric and hybrid-electric propulsion systems. Fully electrifying aviation or all-electric aircraft (AEA) requires high-power density and low-system mass electric power systems (EPS) and MVDC emerges as a viable solution to address this critical need. Multilayer Multifunctional electrical Insulation (MMEI) systems can be a solution to address challenges towards higher voltages and higher density designs under aviation harsh environments. Many MMEI systems have been designed in our earlier work. However, only experimental testing can ascertain the intended MMEI systems' electrical insulation performance. This study presents an optimal approach to fabricating the flat samples of down-selected MMEI designs by a compression-molding process and is discussed in detail. For evaluating different fabrication approaches to determine the optimal one, partial discharge levels of built samples are measured and compared.

关键词： Fabrication Insulation Power cables Transportation Prototypes Nonhomogeneous media Power systems

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Thermal management challenges and approaches for liquid hydrogen-fueled aircraft

Thermal management challenges and approaches for liquid hydr...

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AIAA Aviation Forum and ASCEND, 2024

作者： Ordonez, Juan C. Sailabada, Chaianan Guo, Wei Cooley, Lance Cheetham, Peter Kim, Chul Zheng, Jim P. Gladin, Jonathan Cattafesta, Louis FAMU-FSU College of Engineering Department of Mechanical Engineering Center for Advanced Power Systems and Energy and Sustainability Center Florida State University TallahasseeFL32310 United States Electrical and Computer Engineering FAMU-FSU College of Engineering and Center for Advanced Power Systems Florida State University TallahasseeFL32310 United States Center for Advanced Power Systems FAMU-FSU College of Engineering and Center for Advanced Power Systems Florida State University TallahasseeFL32310 United States Department of Electrical Engineering The State University of New York at Buffalo BuffaloNY14260 United States School of Aerospace Engineering Aerospace Systems Design Laboratory Georgia Institute of Technology AtlantaGA30332 United States Department of Mechanical Materials and Aerospace Engineering Illinois Institute of Technology ChicagoIL60616 United States

ISBN: (数字)9781624107160

ISBN: (纸本)9781624107160

This paper presents an overview of thermal management challenges associated with aircraft that rely on liquid hydrogen as the sole fuel source. The paper discusses strategies that can enhance the overall cooling capacity and enable a larger contribution of fuel cells to the overall power. design considerations for heat exchangers to integrate cryogenic hydrogen with secondary thermal management loops, outer mold line cooling, and additional thermal management strategies are presented. Cooling requirement estimates for a blended-wing aircraft (112 passengers, 2400 nautical miles) are reported. A finite element simulation using RANS suggests a cooling capacity rate of the order of 10 kW/m2 is available through the Outer Mold Line (OML). The paper also reports on the cooling capacity available by using hydrogen as a heat sink to cool the power train. For the IZEA concept, the hydrogen stream to the fuel cell can handle close to 6% of the fuel cell heat generation. © 2024, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.

关键词： Hydrogen fuels

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Fabrication Optimization and PD Characteristics of MVDC Multilayer Insulation Cable systems for Envisaged Wide-Body All-Electric Aircraft

Fabrication Optimization and PD Characteristics of MVDC Mult...

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IEEE Kansas Power and Energy Conference

作者： Md Asifur Rahman Anoy Saha Mona Ghassemi Jane Lehr Department of Electrical and Computer Engineering Zero Emission Realization of Optimized Energy Systems (ZEROES) Laboratory The University of Texas at Dallas Richardson TX USA Department of Electrical and Computer Engineering University of New Mexico Albuquerque UM USA

ISBN: (数字)9798350372403

ISBN: (纸本)9798350372410

Electrifying the aviation sector, a key source of greenhouse gas (GHG) emissions, is critical for the United States to reach its net zero emissions target by 2050. The proposed all-electric aircraft (AEA) will need an electric power system (EPS) that offers high power density and low system mass, making medium voltage DC (MVDC) a better option than existing low voltage systems. The design and fabrication of power cables are pivotal for MVDC due to the thermal challenges the power cables face as a result of the low pressure (18.8 kPa) at a cruising altitude of wide-body passenger aircraft (12.2 km). The temperature distribution along the aircraft cable, largely determined by pressure, surface emissivity, and the shape of the surrounding surfaces, is expected to differ from that at atmospheric pressure because of the reduced heat transfer at lower pressure. In this regard, numerous designs of multilayer multifunctional electrical insulation (MMEI) systems have been presented in our earlier works and can satisfy these requirements. The optimal fabrication process of flat insulation samples of ARC-SC-T-MMEI design has been presented in our earlier work. This paper presents the optimized fabrication process of the cable configuration of ARCSC-T-MMEI design with aluminum hollow tube conductors by compression molding process.

关键词： Fabrication Temperature distribution Power cables Shape Power cable insulation Prototypes Nonhomogeneous media

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