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Resource-constrained maximum network throughput on space networks

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Journal of Systems Engineering and Electronics 2015年第2期26卷 215-223页

作者： Yanling Xing ning ge Youzheng Wang Department of Electronic Engineering Tsinghua University Research Institute of Tsinghua University in Shenzhen Department of Aeronautics and Astronautics Engineering Tsinghua University

This paper investigates the maximum network through- put for resource-constrained space networks based on the delay and disruption-tolerant networking （DTN） architecture. Specifically, this paper proposes a methodology for calculating the maximum network throughput of multiple transmission tasks under storage and delay constraints over a space network. A mixed-integer linear programming （MILP） is formulated to solve this problem. Simula- tions results show that the proposed methodology can successfully calculate the optimal throughput of a space network under storage and delay constraints, as well as a clear, monotonic relationship between end-to-end delay and the maximum network throughput under storage constraints. At the same time, the optimization re- sults shine light on the routing and transport protocol design in space communication, which can be used to obtain the optimal network throughput.

关键词： throughput disruption-tolerant networking(DTN) maximum flow mixed-integer linear programming evolving graph space network

Analysis of swirling flow effects on the characteristics of unsteady hot-streak migration

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Chinese Journal of Aeronautics 2016年第6期29卷 1469-1476页

作者： Wang Jingyu ge ning Sheng Chunhua Nanjing University of Aeronautics and Astronautics Nanjing 210016China Sun Yat-Sen University Guangzhou 510275China The University of Toledo OH 43606USA

The temperature of flow at the combustor exit is inherently non-uniform and the hot fluid is called hot-streak. An in-house CFD software, NUAA-Turbo, was used to carry out 3D unsteady simulations on the PW-Esingle-stage high-pressure turbine. The hot-streak effect based on real stator and combustor counts was approximately evaluated by the contraction/dilatation method on the interface. The unsteady attenuation and migration process of hot-streaks in the turbine passage were well captured. The general performance parameters for different circumferential positions of hot-streaks were relatively consistent. Then, the influences of hot-streaks on blade surface temperature were investigated by comparing results under hot-streak and uniform inflow conditions. Unsteady simulations with combined inlet hot-streak and swirling flow show that the core of a hot-streak migrates to the tip under the influence of a positive swirl, while the phenomenon is just opposite with a negative swirl. Therefore, the heat transfer environment of rotor blades shows great differences with different directions of inlet swirl.

关键词： High pressure turbine Hot-streak Interface contraction/dilatation Swirling flow Unsteady flow

Fast Remote-Sensing Image Registration Using Priori Information and Robust Feature Extraction

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Tsinghua Science and Technology 2016年第5期21卷 552-560页

作者： Xijia Liu Xiaoming Tao ning ge Department of Electronic Engineering Tsinghua University Beijing 100084 China

In this paper, we propose a fast registration scheme for remote-sensing images for use as a fundamental technique in large-scale online remote-sensing data processing tasks. First, we introduce priori-information images,and use machine learning techniques to identify robust remote-sensing image features from state-of-the-art ScaleInvariant Feature Transform（SIFT） features. Next, we apply a hierarchical coarse-to-fine feature matching and image registration scheme on the basis of additional priori information, including a robust feature location map and platform imaging parameters. Numerical simulation results show that the proposed scheme increases position repetitiveness by 34%, and can speed up the overall image registration procedure by a factor of 7：47 while maintaining the accuracy of the image registration performance.

关键词： remote sensing image registration priori information feature extraction

Social-Aware Cooperation Among Mobile Terminals for Wireless Downlink Transmission

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China Communications 2015年第9期12卷 1-10页

作者： Mao Hongliang Feng Wei ge ning Tsinghua National Lab for Information Science and Technology Tsinghua University

This paper investigates the social-aware cooperation(SAC) among mobile terminals(MTs), motivated by the fact that modern smart devices have much improved context awareness. Aware of the social ties, the cooperative network contains two layers of property: social and physical. In order to observe how the social awareness benefit the cooperation performance, we first formulate the social ties between MTs into parameters that can describe the cooperative behaviors by taking the mobility feature into account, defined as the conviction-approval-suspicion(CAS) model. Limited by the processing capability, partner selection is of great practical significance. To this end, the social-aware partner selection strategy is analyzed, and a significant superiority is observed compared to social-unaware selection. By analyzing the cooperative throughput, an explicit relationship between the degrees-of-freedom gain and the social-physical property is finally derived. Simulation results validate the theoretical analysis.

关键词： social-aware cooperation partner selection degrees-of-freedom

Design of Personal Terminal DNS Agent

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Journal of Communications and Information Networks 2021年第3期6卷 251-266页

作者： Yongjia Liu Yu Jiang ning ge The Department of Electronic Engineering Tsinghua UniversityBeijing 100080China

As one of the most important Internet infrastructures,domain name system(DNS)is vulnerable to various attacks,and the issue of DNS security has received critical ***,most of the existing DNS security enhancements have encountered great difficulties in the process of *** main reason is that these enhancement measures usually focus on the server side,thus requiring changes to existing DNS protocol or architecture,while modifying the Internet infrastructure is inherently *** that the range of domain name frequently visited by a single user is much smaller than the entire domain system,in this paper we propose the idea of personal DNS agent(P-DNS),which migrates DNS security from servers to user terminals and can be applied without changing the current DNS infrastructure.P-DNS takes advantage of static and dynamic redundancy to enhance DNS ***,in the static redundancy phase,P-DNS improves the resolution efficiency by utilizing resolution results cached in *** in the dynamic redundancy stage,F-DNS improves the reliability of resolution results by querying multiple recursive name servers(RNSs).Simulation results show that our proposed architecture can effectively improve DNS security performance and greatly reduce the additional delay caused by redundancy.

关键词： DNS security terminal agent fault tolerance

Unsteady supercritical/critical dual flowpath inlet flow and its control methods

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Chinese Journal of Aeronautics 2017年第6期30卷 1877-1884页

作者： Jun LIU Huacheng YUAN Yunfei WANG ning ge College of Energy and Power Engineering Nanjing University of Aeronautics and AstronauticsNanjing 210016China Jiangsu Province Key Laboratory of Aerospace Power Systems Nanjing 210016China

The characteristics of unsteady flow in a dual-flowpath inlet, which was designed for a Turbine Based Combined Cycle（TBCC） propulsion system, and the control methods of unsteady flow were investigated experimentally and numerically. It was characterized by large-amplitude pressure oscillations and traveling shock waves. As the inlet operated in supercritical condition,namely the terminal shock located in the throat, the shock oscillated, and the period of oscillation was about 50 ms, while the amplitude was 6 mm. The shock oscillation was caused by separation in the diffuser. This shock oscillation can be controlled by extending the length of diffuser which reduces pressure gradient along the flowpath. As the inlet operated in critical condition, namely the terminal shock located at the shoulder of the third compression ramp, the shock oscillated,and the period of oscillation was about 7.5 ms, while the amplitude was 12 mm. At this condition,the shock oscillation was caused by an incompatible backpressure in the bleed region. It can be controlled by increasing the backpressure of the bleed region.

关键词： Airbreathing hypersonic vehicle Dual flowpath inlet Terminal shock oscillation Turbine based combined cycle Unsteady flow

Focusing on the meso-scales of multi-scale phenomena-In search for a new paradigm in chemical engineering

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Particuology 2010年第6期8卷 634-639页

作者： Jinghai Li Wei ge Wei Wang ning Yang The EMMS Group State Key Laboratory of Multiphase Complex Systems Institute of Process Engineering Chinese Academy of Sciences Beijing 100190 China

To celebrate the 90th birthday of Professor Mooson Kwauk, who supervised the multi-scale research at this Institute in the last three decades, we dedicate this paper outlining our thoughts on this subject accumulated from our previous studies. In the process of developing, improving and extending the energy- minimization multi-scale （EMMS） method, we have gradually recognized that meso-scales are critical to the understanding of the different kinds of multi-scale structures and systems. It is a common challenge not only for chemical engineering but also for almost all disciplines of science and engineering, due to its importance in bridging micro- and macro-behaviors and in displaying complexity and diversity. It is believed that there may exist a common law behind meso-scales of different problems, possibly even in different fields. Therefore, a breakthrough in the understanding of meso-scales will help materialize a revolutionary progress, with respect to modeling, computation and application.

关键词： Meso-scale Multi-scale Complex system EMMS Multi-phase High performance computation

DDoS Detection for 6G Internet of Things: Spatial-Temporal Trust Model and New Architecture

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China Communications 2022年第5期19卷 141-149页

作者： Yinglun Ma Xu Chen Wei Feng ning ge Department of Electronic Engineering Tsinghua UniversityBeijing 100084China Beijing National Research Center for Information Science and Technology Beijing 100084China

With the rapid development of the sixth generation(6G)network and Internet of Things(IoT),it has become extremely challenging to efficiently detect and prevent the distributed denial of service(DDoS)attacks originating from IoT *** this paper we propose an innovative trust model for IoT devices to prevent potential DDoS attacks by evaluating their trustworthiness,which can be deployed in the access network of 6G *** on historical communication behaviors,this model combines spatial trust and temporal trust values to comprehensively characterize the normal behavior patterns of IoT devices,thereby effectively distinguishing attack *** results show that the proposed method can efficiently distinguish normal traffic from DDoS *** with the benchmark methods,our method has advantages in terms of both accuracy and efficiency in identifying attack flows.

关键词： sixth generation(6G)network internet of things(IoT) trust model distributed denial of service(DDoS)

Robustness Evaluation of Remote-Sensing Image Feature Detectors with TH Priori-Information Data Set

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China Communications 2020年第10期17卷 218-228页

作者： Yiping Duan Xiaoming Tao Xijia Liu ning ge Department of Electronic Engineering Tsinghua UniversityBeijing 100084China Beijing National Research Center for Information Science and Technology Beijing 100084China

In this paper,we build a remote-sensing satellite imagery priori-information data set,and propose an approach to evaluate the robustness of remote-sensing image feature *** building TH Priori-Information(TPI)data set with 2297 remote sensing images serves as a standardized high-resolution data set for studies related to remote-sensing image *** TPI contains 1)raw and calibrated remote-sensing images with high spatial and temporal resolutions(up to 2 m and 7 days,respectively),and 2)a built-in 3-D target area model that supports view position,view angle,lighting,shadowing,and other *** on TPI,we further present a quantized approach,including the feature recurrence rate,the feature match score,and the weighted feature robustness score,to evaluate the robustness of remote-sensing image feature *** quantized approach gives general and objective assessments of the robustness of feature detectors under complex remote-sensing *** remote-sensing image feature detectors,including scale-invariant feature transform(SIFT),speeded up robust features(SURF),and priori information based robust features(PIRF),are evaluated using the proposed approach on the TPI data *** results show that the robustness of PIRF outperforms others by over 6.2%.

关键词： remote-sensing TH data set image feature robustness evaluation