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AIAA science and technology Forum and Exposition, AIAA SciTech Forum 2021

作者： Qin, Decong Chen, Haibing Lin, Wei Tang, Peng Ma, Tielin Xu, Cheng School of Transportation Science and Engineering Beihang University Beijing China Aircraft/Engine Integrated System Safety Beijing Key Laboratory Beijing China Beijing System Design Institute of the Electro-mechanic Engineering Beijing China Institute of Unmanned System Beihang University Beijing China Science and Technology on Complex System Control and Intelligent Agent Cooperation Laboratory Beijing China

ISBN: (纸本)9781624106095

Flexible air-breathing hypersonic vehicles show significant and complex aerodynamic, scramjet propulsion system, flight dynamic and elastic coupling characteristics, which usually are highly nonlinear. These result in huge uncertainties, parameter perturbation and internal disturbance, which can no longer be ignored, and therefore, extreme difficulties for flight control design. A unique parameter adaptive non-singular terminal sliding mode method is proposed for longitudinal control law design of a flexible coupling air-breathing hypersonic vehicle. This method uses adaptive reaching law gain instead of additional adaptive compensation term to handle the uncertainty to improve robustness. The stability of the close loop system is proved via a Lyapunov way. The longitudinal tracking control law for velocity and angle of attack is designed based on a rigid dynamic model of a flexible air-breathing hypersonic vehicle. A strong coupling model of the same vehicle, considering aerodynamic-scramjet engine-flight dynamic-elastic couplings, is established as the verification platform of control law designed. Simulation results obtained based on the coupling model demonstrate that the control law designed has good performance and acceptable robustness. © 2021, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.

关键词： Hypersonic vehicles

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Comparative Analysis of a Proposed Low-Power Adiabatic NOR Gate

Comparative Analysis of a Proposed Low-Power Adiabatic NOR G...

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International Conference on Computer and Information technology (ICCIT)

作者： Chamak Ganguly Mazeda Zafor Meem Mohammed Abdullah Faruque S. M Kifayat Kabir Saeed Hossen Rakib Khandaker Shams Arefin Dept. of EEE Primeasia University Dhaka Bangladesh Dept. of EEE Ahsanullah University of Science and Technology Dhaka Bangladesh Circuit and System Design ULKASEMI Pvt. Limited Dhaka Bangladesh Physical Design Neural Semiconductor Limited Dhaka Bangladesh

This paper discusses the low-power adiabatic models because the power and energy consumption increase of our used devices has become significant. In this thought, the solution of using the battery has become complex as a scale-down battery means a low power supply has to be given, and the threshold voltage of the transistors has to decrease. Techniques like multi-threshold devices (MTCMOS), variable multi-threshold devices (VTCMOS), and dynamic threshold devices (DTCMOS) come forward to mitigate the high-power consumption, which results in thinner gate-oxide, gate leakage, and power dissipation. The adiabatic technique is also one of the methods for reducing power in a device where a pulsating AC voltage is used instead of a constant voltage supply. This study proposes an adiabatic circuit for a NOR gate using a 32nm LP PTM Model. The comparative study, among the proposed circuit and PFAL, IPFAL, 2n2n2p, and ECRL used industry-standard software Cadence and LTSpice. Results show outstanding performance in power and energy dissipation as well as lower propagation delay in terms of the proposed inverter circuit, which is approximately 5.61% less than the adiabatic circuit 2N2N2P at 100MHz which has the lowest propagation delay other than the proposed inverter circuit. Power dissipation is reduced up to 77% in the proposed inverter circuit compared to the 2N2N2P adiabatic inverter circuit, which provides lower power among all the adiabatic circuits used in the experiment at 25MHz frequency. Similarly, the power dissipation for the proposed NOR circuit becomes 93% less than ECRL, which shows the lowest results after the proposed circuit at 25MHz frequency.

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A Miniaturized and Packaged LTCC Filtering Balun Using Lumped Elements

A Miniaturized and Packaged LTCC Filtering Balun Using Lumpe...

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IEEE MTT-S International Microwave Workshop Series on Advanced Materials and Processes for RF and THz Applications (IMWS-AMP)

作者： Bingfang Xu Chonggang Yang Peiyao Chen Henghui Wang Xianzheng Zong Sheng Sun School of Electronic Science and Engineering University of Electronic Science and Technology of China Chengdu China Avionics System Design Department AVIC the First Aircraft Institute Xi'an China

In this paper, a low temperature co-fired ceramic (LTCC) filtering balun based on lumped elements is presented. It is composed of a lumped filter and a lumped balun cascaded via a vertical metal through-hole. The filtering balun operates at 2.45 GHz with the fractional bandwidth of 15%. Within the passband, simulated results demonstrate that the magnitude difference and phase difference of the filtering balun are within 0.4 dB and 5°, respectively. Frequency selection characteristics and balanced-to-unbalanced conversion are well achieved, and its package size is 4.8 mm × 4.2 mm × 1.5 mm or 0.095λ g × 0.083λ g × 0.029λ g .

关键词： Radio frequency Filtering Baluns Conferences Metals Bandwidth Frequency conversion

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Generative Models are Self-Watermarked: Declaring Model Authentication through Re-Generation

arXiv

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arXiv 2024年

作者： Desu, Aditya He, Xuanli Xu, Qiongkai Lu, Wei School of Computing and Information System University of Melbourne Melbourne Australia Department of Computer Science University College London United Kingdom School of Computing FSE Macquarie University Sydney Australia StatNLP Research Group Singapore University of Technology and Design Singapore

As machine- and AI-generated content proliferates, protecting the intellectual property of generative models has become imperative, yet verifying data ownership poses formidable challenges, particularly in cases of unauthorized reuse of generated data. The challenge of verifying data ownership is further amplified by using Machine Learning as a Service (MLaaS), which often functions as a black-box system. Our work is dedicated to detecting data reuse from even an individual sample. Traditionally, watermarking has been leveraged to detect AI-generated content. However, unlike watermarking techniques that embed additional information as triggers into models or generated content, potentially compromising output quality, our approach identifies latent fingerprints inherently present within the outputs through re-generation. We propose an explainable verification procedure that attributes data ownership through regeneration, and further amplifies these fingerprints in the generative models through iterative data re-generation. This methodology is theoretically grounded and demonstrates viability and robustness using recent advanced text and image generative models. Our methodology is significant as it goes beyond protecting the intellectual property of APIs and addresses important issues such as the spread of misinformation and academic misconduct. It provides a useful tool to ensure the integrity of sources and authorship, expanding its application in different scenarios where authenticity and ownership verification are essential. © 2024, CC BY-NC-ND.

关键词： Authentication

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Pale Red Dot: A Large, Robust Architecture for Human Settlements on Mars

Pale Red Dot: A Large, Robust Architecture for Human Settlem...

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Accelerating Space Commerce, Exploration, and New Discovery Conference, ASCEND 2023

作者： Lordos, George Hoying, Madelyn McKinney, Lanie Webb, Alisa Lin, Yuying Martin, Estelle Beilstein, John Miller, Duncan Villegas, David Sepulveda, Francisco AlSadah, Yousif Iyer, Divya O’Neill, Cormac Patel, Palak Garcia, Ignacio Arzuaga Azzouz, H. Chan, Wing Lam Eyre, Ezra Gleason, Dane Romero, Elizabeth Arias, Liliana Orozco, Omar Gentgen, Chloe Latyshev, Kir Hoffman, Jeffrey de Weck, Olivier Ikinci, Meltem Lordos, Alexandros Aeronautics and Astronautics Massachusetts Institute of Technology 33-409 CambridgeMA02139 United States Massachusetts Institute of Technology Harvard-MIT Health Sciences and Technology Program and MIT Aeronautics and Astronautics 33-409 CambridgeMA02139 United States Massachusetts Institute of Technology CambridgeMA02139 United States Aeronautics and Astronautics Massachusetts Institute of Technology 77 Mass Ave. 33-409 CambridgeMA02139 United States System Design and Management Massachusetts Institute of Technology 77 Mass Ave. E40-300 CambridgeMA02139 United States Mechanical Engineering Massachusetts Institute of Technology 77 Mass Ave. 33-409 CambridgeMA02139 United States Civil and Environmental Engineering Massachusetts Institute of Technology 77 Mass Ave. CambridgeMA02139 United States Electrical Engineering Massachusetts Institute of Technology 77 Mass Ave. CambridgeMA02139 United States Nuclear Science and Engineering Massachusetts Institute of Technology 77 Mass Ave. CambridgeMA02139 United States Computer Science and Engineering Massachusetts Institute of Technology 77 Mass Ave. CambridgeMA02139 United States Massachusetts Institute of Technology 77 Mass Ave. 37-219 CambridgeMA02139 United States Massachusetts Institute of Technology 77 Mass Ave. 33-410 CambridgeMA02139 United States Behavioral Economics University of Cyprus Nicosia Cyprus Department of Psychology University of Cyprus Nicosia Cyprus

ISBN: (数字)9781624107054

ISBN: (纸本)9781624107054

We propose a ten-yearMars mission to establish Earth-independence and support efficient, safe, and sustainable science and exploration goals. The campaign begins with a series of precursor missions, starting with the Artemis program, followed by robotic missions to performsite surveys and selection, de-risk technologies, and to start stockpiling in-situ water and propellant. Robotic Cargo Starships would depart first in 2035 to deliver and deploy approximately 5,800 tons of habitats, nuclear microreactors, farmmodules, manufacturing and ISRU systems. In 2040, two Crew Starships carrying 36 persons would land onMars to establish two close-proximity villages. The lifecycle cost is estimated at $81 billion, with a peak annual cost of $6.6 billion. To meet RASC-AL competition requirements, intended to motivate the exploration of highly self-reliant architecture concepts, resupply from Earth was constrained to only 5 metric tons every two years and minimum surface endurance was set at 7 years. The risks to human life and to critical systems increase exponentially over a minimally-resupplied, 7-10 year mission toMars. Our approach focused on identifying capabilities to mitigate known and unknown risks. Using a high-fidelity crew time model, we found that large architectures, with their economies of scale and productivity gains from specialization, are essential to robustly support the necessary capabilities. The model also shows that small 7-year missions of 12 persons or less cannot provide value in terms of free surface traverse time for science and exploration. Given the necessity of a large, complex architecture, we then sought out efficiencies and synergies (value engineering) in order to make the mission feasible and affordable. In the process, we identified more benefits that are enabled only by large missions, including the creation of a true community on Mars with sufficient social complexity for humans to thrive, and the geopolitically compelling option to inclu

关键词： Value engineering

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Bioinspired hierarchical helical nanocomposite macrofibers based on bacterial cellulose nanofibers

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National science Review 2020年第1期7卷 73-83页

作者： Huai-Ling Gao Ran Zhao Chen Cui Yin-Bo Zhu Si-Ming Chen Zhao Pan Yu-Feng Meng Shao-Meng Wen Chuang Liu Heng-An Wu Shu-Hong Yu Division of Nanomaterials & Chemistry Hefei National Laboratory for Physical Sciences at the Microscale CAS Center for Excellence in Nanoscience Hefei Science Center of CAS Department of Chemistry University of Science and Technology of China CAS Key Laboratory of Mechanical Behavior and Design of Materials Department of Modern Mechanics CAS Center for Excellence in Complex System Mechanics University of Science and Technology of China

Bio-sourced nanocellulosic materials are promising candidates for spinning high-performance sustainable macrofibers for advanced applications. Various strategies have been pursued to gain nanocellulose-based macrofibers with improved strength. However, nearly all of them have been achieved at the expense of their elongation and toughness. Inspired by the widely existed hierarchical helical and nanocomposite structural features in biosynthesized fibers exhibiting exceptional combinations of strength and toughness, we report a design strategy to make nanocellulose-based macrofibers with similar characteristics. By combining a facile wet-spinning process with a subsequent multiple wet-twisting procedure, we successfully obtain biomimetic hierarchical helical nanocomposite macrofibers based on bacterial cellulose nanofibers, realizing impressive improvement in their tensile strength, elongation and toughness simultaneously. The achievement certifies the validity of the bioinspired hierarchical helical and nanocomposite structural design proposed here. This bioinspired design strategy provides a potential platform for further optimizing or creating many more strong and tough nanocomposite fiber materials for diverse applications.

关键词： bioinspired nanocomposite hierarchical helical macrofibers strength and toughness bacterial cellulose

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Numerical comparison of transpiration cooling designs using real gas effects and approximate gas model

Numerical comparison of transpiration cooling designs using ...

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2021 International Conference on Fluid and Chemical Engineering, ICFCE 2021

作者： Wang, Meng Wang, Jianhua He, Fei Qian, Kang Wu, Yadong Zhu, Guangsheng CAS Key Laboratory of Mechanical Behaviour and Design of Materials Department of Thermal Science and Energy Engineering University of Science and Technology of China Anhui Hefei230027 China Beijing Institute of Astronautical System Engineering Beijing100076 China

In the severe high-temperature environment caused by aerodynamic heating, the vibrational excitation, dissociation and ionization of gas may successively occur, which are known as real gas effects. Under the real gas effects, the thermodynamic properties of gas vary drastically and significantly influence the performances of the active thermal protection system of hypersonic vehicles, especially in the case with coolant outflow, for example transpiration cooling. This paper numerically investigates the transpiration cooling performance with the consideration of the interaction between coolant outflow and hypersonic flow under the real gas effects. The mathematical models and coupled numerical strategy are firstly validated by experimental data, then the influences of real gas effects on the transpiration cooling of a wedged leading edge (WLE) are studied under a flight Mach number range from 8 to 12 and a flight height of 40 km. The analysis and discussions of the numerical results reveal some important phenomena and demonstrate the need to consider real gas effects.

关键词： Hypersonic vehicles

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Anti-Fatigue Nanomechanics in the Pre-Cracked Graphene-Copper Artificial Nacre Under Cyclic Tension

SSRN

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SSRN 2023年

作者： Liu, Xiaoyi Xu, Yunfei Shi, Jinchun Zhu, YinBo Zhang, Sen Wu, HengAn Mechanics+X Laboratory Chengdu Development Center of Science and Technology China Academy of Engineering Physics Chengdu610200 China CAS Key Laboratory of Mechanical Behavior and Design of Materials Department of Modern Mechanics CAS Center for Excellence in Complex System Mechanics University of Science and Technology of China Hefei230027 China

The fatigue performance of pre-cracked graphene-copper artificial nacre (GrCu nacre) under cyclic tensile loading is investigated using theoretical analysis and molecular dynamics (MD) simulations. Mechanical models are proposed to describe the fatigue performance of GrCu nacre, which agree well with MD simulations. Compared with nanocomposites consisting of large graphene sheets, graphene fragments cannot improve the ultimate strength of GrCu nacre, but significantly improve its fatigue limit. This anti-fatigue effect is dominated by the graphene-copper interfaces with van der Waals interactions, which can be adjusted by tailoring the architectural parameters of GrCu nacre. The ultimate strength of nacre decreases as the volume fraction of graphene increases. The fatigue limit of GrCu nacre decreases as the length of graphene fragments increases, and can be approximately described by a quadratic function of interlayer repeat spacing. An anomalous weakening effect occurs when the in-plane distance between graphene fragments is less than 2 nm, while this effect can be ignored when it is higher than 2 nm. The fatigue ratio of common metals is ~0.4, whereas that of GrCu nacre is generally higher than 0.9. These underlying mechanisms and theoretical models can improve the fundamental understanding of the fatigue performance of composites with incoherent interfaces, as well as the bottom-up design of graphene-metal nanocomposites. © 2023, The Authors. All rights reserved.

关键词： Molecular dynamics

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Numerical Simulation of Flow-Thermal Coupling Field Inside Upper Plenum and Hot Legs of Pressurized Water reactor (Pwr)

SSRN

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SSRN 2022年

作者： Sun, Ziyun Zhou, Xinzhi He, Zhengxi Xu, Tao Zhu, Jialiang Dong, Chenlong College of Electronics And Information Engineering Sichuan University No. 24 South Section 1 1st Ring Road Sichuan Chengdu China Science and Technology on Reactor System Design Technology Laboratory Nuclear Power Institute of China No. 328 Section 1 Changshun Avenue Sichuan Chengdu China

The temperature and flow rate of coolant in the hot legs of pressurized water reactor (PWR) systems directly reflect the nuclear power and the heat transfer state of the reactor core, and are key parameters for reactor power control and safety protection. Most of existing studies have been conducted to analyze the steady-state thermal hydraulic features in the upper plenum and hot legs from a spatial scale, but less from a temporal scale to describe and analyze the transient features. In order to meet the requirements of key parameters measurement and safe operation, this paper established a reasonably simplified 3D geometrical model of the upper plenum and hot legs of the HPR1000 reactor based on a multi-physics field simulation platform and investigated the steady-state and transient features of the flow-thermal coupling field of coolant under numerical simulation, focusing on the coupling analysis of the flow-thermal coupling field on the spatial and temporal scales. The analysis of the steady-state features shows that the coolant flowing into the upper plenum from the upper core plate is characterized by a high middle temperature and a low peripheral temperature. As a result, there is an uneven coolant temperature distribution at the inlet of the hot legs that the temperature differences between the cold lower part and hot upper part are relatively large. However, with the axial flow of coolant, the temperature distribution in hot legs tends to be more uniform and the temperature differences decrease. The simulation results show that the flow of the low temperature coolant in hot legs dominates the change of coolant temperature distribution. The analysis of the transient features shows that a small fluctuation of flow rate at the core outlet causes changes in the turbulent kinetic energy of coolant in hot legs, but the effect on coolant temperature distribution is relatively weak. These such variations on the temporal scale can change the coupling relations of c

关键词： Multiphysics

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CamVox: A Low-cost and Accurate Lidar-assisted Visual SLAM system

CamVox: A Low-cost and Accurate Lidar-assisted Visual SLAM S...

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IEEE International Conference on Robotics and Automation (ICRA)

作者： Yuewen Zhu Chunran Zheng Chongjian Yuan Xu Huang Xiaoping Hong School of System Design and Intelligent Manufacturing Southern University of Science and Technology China

Combining lidar in camera-based simultaneous localization and mapping (SLAM) is an effective method in improving overall accuracy, especially at outdoor large scale scenes. Recent development of low-cost lidars (e.g. Livox lidar) enable us to explore such SLAM systems with lower budget and higher performance. In this paper we propose CamVox by adapting Livox lidars into visual SLAM (ORB-SLAM2) by exploring the lidars’ unique features. Based on the unique scan pattern of Livox lidars, we propose an automatic lidar-camera calibration method that will work in uncontrolled scenes. The long depth detection range also benefit a more accurate mapping. Comparison of CamVox with visual SLAM (VINS-mono) and lidar SLAM (LOAM) are evaluated on the same dataset to demonstrate the performance. We open sourced our hardware, code and dataset on GitHub¹.

关键词： Visualization Simultaneous localization and mapping Laser radar Codes Automation Conferences Hardware

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