National University of Defense Technology

About: National University of Defense Technology is a education organization based out in Changsha, China. It is known for research contribution in the topics: Radar & Synthetic aperture radar. The organization has 39430 authors who have published 40181 publications receiving 358979 citations. The organization is also known as: Guófáng Kēxuéjìshù Dàxué & NUDT.

RLM: A General Model for Trust Representation and Aggregation

Abstract: Reputation-based trust systems provide important capability in open and service-oriented computing environments. Most existing trust models fail to assess the variance of a reputation prediction. Moreover, the summation method, widely used for reputation feedback aggregation, is vulnerable to malicious feedbacks. This paper presents a general trust model, called RLM, for a more comprehensive and robust reputation evaluation. Concretely, we define a comprehensive reputation evaluation method based on two attributes: reputation value and reputation prediction variance. The reputation predication variance serves as a quality measure of the reputation value computed based on aggregation of feedbacks. For feedback aggregation, we propose the novel Kalman aggregation method, which can inherently support robust trust evaluation. To defend against malicious and coordinated feedbacks, we design the Expectation Maximization algorithm to autonomously mitigate the influence of a malicious feedback, and further apply the hypothesis test method to resist malicious feedbacks precisely. Through theoretical analysis, we demonstrate the robustness of the RLM design against adulating and defaming attacks, two popular types of feedback attacks. Our experiments show that the RLM model can effectively capture the reputation's evolution and outperform the popular summation-based trust models in terms of both accuracy and attack resilience. Concretely, under the attack of collusive malicious feedbacks, RLM offers higher robustness for the reputation prediction and a lower false positive rate for the malicious feedback detection.

Proof of Reputation: A Reputation-Based Consensus Protocol for Peer-to-Peer Network

Abstract: The advent of blockchain sheds light on addressing trust issues of peer-to-peer networks by providing a distributed tamper-resistant ledger. Beyond cryptocurrencies, it is believed that blockchain can also be used to protect other properties such as reputation. Most of the existing studies of enhancing reputation systems using blockchains are built on top of the bitcoin-like blockchains, so they are inherently constrained by the low-efficiency and high-consumption of the underlying blockchain. To fill this gap, we present a reputation-based consensus protocol called Proof of Reputation (PoR), which guarantees the reliability and integrity of transaction outcomes in an efficient way. In PoR, we let reputation serves as the incentive for both good behavior and block publication instead of digital coins, therefore no miners are needed. We also implement a prototype and our scalability experiments show that our protocol can scale to over a thousand participants in a peer-to-peer network with throughput of hundreds of transactions per second.

A tunable sound-absorbing metamaterial based on coiled-up space

Abstract: This paper presents a theoretical, numerical, and experimental investigation of a deep-subwavelength absorber based on the concept of coiled-up space. By adjusting a partition panel in the cavity to form an unequal-section channel, it is found that the resonance frequency of the absorber is easily tuned and near-total absorption is acquired under a fixed deep-subwavelength thickness. The absorption mechanism induced by nearly critical coupling is revealed by graphically analyzing the reflection coefficient in the complex plane. In contrast to conventional techniques, near-total absorption can be adjusted over a wider frequency range. To further enhance the absorption, we demonstrate a broadband absorber with a relative bandwidth up to 33.3%.

Gaussian-modulated coherent-state measurement-device-independent quantum key distribution

Abstract: Measurement-device-independent quantum key distribution (MDI-QKD), leaving the detection procedure to the third partner and thus being immune to all detector side-channel attacks, is very promising for the construction of high-security quantum information networks. We propose a scheme to implement MDI-QKD, but with continuous variables instead of discrete ones, i.e., with the source of Gaussian-modulated coherent states, based on the principle of continuous-variable entanglement swapping. This protocol not only can be implemented with current telecom components but also has high key rates compared to its discrete counterpart; thus it will be highly compatible with quantum networks.

Analysis of worst-case delay bounds for best-effort communication in wormhole networks on chip

Abstract: In packet-switched network-on-chip, computing worst-case delay bounds is crucial for designing predictable and cost-effective communication systems but yet an intractable problem due to complicated resource sharing scenarios. For wormhole networks with credit-based flow control, the existence of cyclic dependency between flit delivery and credit generation further complicates the problem. Based on network calculus, we propose a technique for analyzing communication delay bounds for individual flows in wormhole networks. We first propose router service analysis models for flow control, link and buffer sharing. Based on these analysis models, we obtain a buffering-sharing analysis network, which is open-ended and captures both flow control and link sharing. Furthermore, we compute equivalent service curves for individual flows using the network contention tree model in the buffer-sharing analysis network, and then derive their delay bounds. Our experimental results verify that the theoretical bounds are correct and tight.