47 research outputs found
Joint Relay and Jammer Selection for Secure Two-Way Relay Networks
In this paper, we investigate joint relay and jammer selection in two-way
cooperative networks, consisting of two sources, a number of intermediate
nodes, and one eavesdropper, with the constraints of physical layer security.
Specifically, the proposed algorithms select two or three intermediate nodes to
enhance security against the malicious eavesdropper. The first selected node
operates in the conventional relay mode and assists the sources to deliver
their data to the corresponding destinations using an amplify-and-forward
protocol. The second and third nodes are used in different communication phases
as jammers in order to create intentional interference upon the eavesdropper
node. Firstly, we find that in a topology where the intermediate nodes are
randomly and sparsely distributed, the proposed schemes with cooperative
jamming outperform the conventional non-jamming schemes within a certain
transmitted power regime. We also find that, in the scenario in which the
intermediate nodes gather as a close cluster, the jamming schemes may be less
effective than their non-jamming counterparts. Therefore, we introduce a hybrid
scheme to switch between jamming and non-jamming modes. Simulation results
validate our theoretical analysis and show that the hybrid switching scheme
further improves the secrecy rate.Comment: 25 pages, 7 figures; IEEE Transactions on Information Forensics and
Security, 201
Asymmetrical Hierarchical Networks with Attentive Interactions for Interpretable Review-Based Recommendation
Recently, recommender systems have been able to emit substantially improved
recommendations by leveraging user-provided reviews. Existing methods typically
merge all reviews of a given user or item into a long document, and then
process user and item documents in the same manner. In practice, however, these
two sets of reviews are notably different: users' reviews reflect a variety of
items that they have bought and are hence very heterogeneous in their topics,
while an item's reviews pertain only to that single item and are thus topically
homogeneous. In this work, we develop a novel neural network model that
properly accounts for this important difference by means of asymmetric
attentive modules. The user module learns to attend to only those signals that
are relevant with respect to the target item, whereas the item module learns to
extract the most salient contents with regard to properties of the item. Our
multi-hierarchical paradigm accounts for the fact that neither are all reviews
equally useful, nor are all sentences within each review equally pertinent.
Extensive experimental results on a variety of real datasets demonstrate the
effectiveness of our method
Dynamic Gaussian Mixture based Deep Generative Model For Robust Forecasting on Sparse Multivariate Time Series
Forecasting on sparse multivariate time series (MTS) aims to model the
predictors of future values of time series given their incomplete past, which
is important for many emerging applications. However, most existing methods
process MTS's individually, and do not leverage the dynamic distributions
underlying the MTS's, leading to sub-optimal results when the sparsity is high.
To address this challenge, we propose a novel generative model, which tracks
the transition of latent clusters, instead of isolated feature representations,
to achieve robust modeling. It is characterized by a newly designed dynamic
Gaussian mixture distribution, which captures the dynamics of clustering
structures, and is used for emitting timeseries. The generative model is
parameterized by neural networks. A structured inference network is also
designed for enabling inductive analysis. A gating mechanism is further
introduced to dynamically tune the Gaussian mixture distributions. Extensive
experimental results on a variety of real-life datasets demonstrate the
effectiveness of our method.Comment: This paper is accepted by AAAI 202
Energy waste in buildings due to occupant behaviour
Occupants’ behaviour has a significant impact on the energy performance of buildings. A good understanding of how occupants use a building provides a possibility of promoting the building’s energy efficiency through changing occupant behaviour. Building simulation has been adopted as a useful method by building engineers for quantifying the effects of changing occupant behaviour on the building’s energy consumption and indoor environment. However, due to the lack of real measured data with respect to how occupants use the building, such simulation work has relied on assumed behavioural patterns, which significantly reduces the reliability of the predicted results. This paper describes a longitudinal study monitoring occupants’ heating, window opening and cooling behaviour in an office building throughout summer, transitional and winter periods. These behavioural data were then used to drive dynamic building performance simulation to predict the energy saving potential of changing behaviour. Comparison with predicted results by assumed behavioural patterns reflected that improperly assumed behavioural patterns may either overestimate or underestimate the energy saving potential of changing behaviour, especially for unextreme behaviours
A preliminary evaluation of targeted nanopore sequencing technology for the detection of Mycobacterium tuberculosis in bronchoalveolar lavage fluid specimens
ObjectiveTo evaluate the efficacy of targeted nanopore sequencing technology for the detection of Mycobacterium tuberculosis(M.tb.) in bronchoalveolar lavage fluid(BALF) specimens.MethodsA prospective study was used to select 58 patients with suspected pulmonary tuberculosis(PTB) at Henan Chest Hospital from January to October 2022 for bronchoscopy, and BALF specimens were subjected to acid-fast bacilli(AFB) smear, Mycobacterium tuberculosis MGIT960 liquid culture, Gene Xpert MTB/RIF (Xpert MTB/RIF) and targeted nanopore sequencing (TNS) for the detection of M.tb., comparing the differences in the positive rates of the four methods for the detection of patients with different classifications.ResultsAmong 58 patients with suspected pulmonary tuberculosis, there were 48 patients with a final diagnosis of pulmonary tuberculosis. Using the clinical composite diagnosis as the reference gold standard, the sensitivity of AFB smear were 27.1% (95% CI: 15.3-41.8); for M.tb culture were 39.6% (95% CI: 25.8-54.7); for Xpert MTB/RIF were 56.2% (95% CI: 41.2-70.5); for TNS were 89.6% (95% CI: 77.3-96.5). Using BALF specimens Xpert MTB/RIF and/or M.tb. culture as the reference standard, TNS showed 100% (30/30) sensitivity. The sensitivity of NGS for pulmonary tuberculosis diagnosis was significantly higher than Xpert MTB/RIF, M.tb. culture, and AFB smear. Besides, P values of <0.05 were considered statistically significant.ConclusionUsing a clinical composite reference standard as a reference gold standard, TNS has the highest sensitivity and consistency with clinical diagnosis, and can rapidly and efficiently detect PTB in BALF specimens, which can aid to improve the early diagnosis of suspected tuberculosis patients
The Tianlai Cylinder Pathfinder array: System functions and basic performance analysis
The Tianlai Cylinder Pathfinder is a radio interferometer array designed to test techniques for 21 cm intensity mapping in the
post-reionization Universe, with the ultimate aim of mapping the large scale structure and measuring cosmological parameters
such as the dark energy equation of state. Each of its three parallel cylinder reflectors is oriented in the north-south direction, and
the array has a large field of view. As the Earth rotates, the northern sky is observed by drift scanning. The array is located in
Hongliuxia, a radio-quiet site in Xinjiang, and saw its first light in September 2016. In this first data analysis paper for the Tianlai
cylinder array, we discuss the sub-system qualification tests, and present basic system performance obtained from preliminary
analysis of the commissioning observations during 2016-2018. We show typical interferometric visibility data, from which we
derive the actual beam profile in the east-west direction and the frequency band-pass response. We describe also the calibration
process to determine the complex gains for the array elements, either using bright astronomical point sources, or an artificial on
site calibrator source, and discuss the instrument response stability, crucial for transit interferometry. Based on this analysis, we
find a system temperature of about 90 K, and we also estimate the sensitivity of the array
Preparation of graphene, bismuth chalcogenide and their heterostructures with application in photonics and optoelectronics
Graphene, a novel 2-D
allotrope form of carbon, has triggered intensive research interests in 2-D materials. 2-D materials’ extraordinary properties
promise varies applications, such as electronics, optics and optoelectronics. Particularly,
graphene and bismuth chalcogenides (Bi<sub>2</sub>Se<sub>3</sub>, Bi<sub>2</sub>Te<sub>3</sub> et. al.), which share similar Dirac bandgap
structures and exotic surface states, are outstanding candidates in potential applications of
broadband optoelectronic, plasmonic devices and future on-chip devices. Though researchers have
dedicated their efforts in the 2-D materials, the attention being paid to the graphene and
bismuth chalcogenides based materials remains low, especially in their large production and
optoelectronic device applications. <br>
   This research dissertation starts with the preparation of
high quality graphene, bismuth chalcogenide nanocrystals and their heterostructure. By
taking advantages of the <i>in situ</i> Powder X-ray diffraction technique, better understanding in the
growth mechanism of bismuth chalcogenides nanoplatelets and its graphene heterostructure
has been obtained. Step by step growth mechanism is revealed and discussed. Thus large-scale
prepared graphene and bismuth chalcogenides hybrid material has been integrated into a free
standing thin film, which is further demonstrated as a broadband photodetector. On the
other hand, it is found that the graphene and Bi<sub>2</sub>Te<sub>3</sub> heterostructure films can effectively
enhance plasmon resonance magnitude in its FTIR spectrum by increasing light-matter
interactions. In order to better observe and understand the plasmonic resonance modes on these
materials, the later sections of this dissertation investigated resonance modes on graphene
surfaces from both far-field and near-field. The results show that the light-matter interaction
can be further enhanced by modifying the geometry of the surface and the surface plasmon
can be guided in a controlled manner. It is believed, this dissertation paves way for the
photonic and optoelectronic researches of graphene, bismuth chalcogenides and their heterostructures
Dynamic Modeling and Analysis of Thrust Reverser Mechanism Considering Clearance Joints and Flexible Component
As a high-precision motion mechanism, the kinematics and dynamics of cascade thrust reverser are sensitive to the changes of nonlinear factors which are rarely considered in traditional dynamic modeling and optimization. In order to study the effect of nonlinear factors on the dynamics behavior of cascade thrust reverser mechanism, the dynamic model considering joint clearance and flexible component is established. Lankarani–Nikravesh and modified-Coulomb model are used to establish the contact force at the clearance, and the flexible component in the mechanism is modeled by the absolute node coordinate method. The effects of joint clearance value, clearance position, flexible component, and driving speed on the dynamic response of the mechanism are studied. Specifically, the nonlinear characteristics of the mechanism increase with the clearance value, and the joint clearance near the mobile fairing has greater influence on the kinematics and dynamics of blocker door. For the mechanical system with clearances, the flexible component can partially reduce the vibration of the system. The analysis of the motion synchronization of the thrust reverser actuators indicates that the asynchronous movement of actuators may increase the driving forces of actuators especially for the middle actuator
A novel stepwise catheter ablation method of the mitral isthmus for persistent atrial fibrillation: efficacy and reproducibility
Abstract Background Ethanol infusion of the vein of Marshall (EI-VOM) has been widely used to facilitate mitral isthmus (MI) ablation. According to the literature, the success rate of achieving a bidirectional conduction block across the MI ranges from 51 to 96%, with no standardized strategy or method available for cardiac electrophysiologists. Objectives This study aimed to introduce and evaluate a novel ablation method of MI. Methods Consecutive patients with persistent atrial fibrillation (PeAF) that underwent catheter ablation were included. The MI ablation procedure followed a stepwise approach. In step 1, ethanol infusion of the vein of Marshall (EI-VOM) was performed. In step 2, a “V-shape” endocardial linear ablation connecting the left inferior pulmonary vein (LIPV) to mitral annulus (MA) was performed. In step 3, earliest activation sites(EASs) near the ablation line were identified using activation mapping followed by reinforced ablation. In step 4, precise epicardial ablation was performed, with the catheter introduced into the coronary sinus(CS) to target key ablation targets (KATs). Results 135 patients with PeAF underwent catheter ablation with the stepwise ablation method adopted in 119 cases. Bidirectional conduction blocks were achieved in 117 patients (98.3%). The block rates of every step were 0%, 58.0%, 44.0%, and 92.9%, and the cumulative block rates for the four steps were 0%, 58.0%, 76.5%, and 98.3%, respectively. No patient experienced fatal complications. Conclusions Our novel stepwise catheter ablation method for MI yielded a high bidirectional block rate with high reproducibility