329 research outputs found
Cascaded Entanglement Enhancement
We present a cascaded system consisting of three non-degenerate optical
parametric amplifiers (NOPAs) for the generation and the enhancement of quantum
entanglement of continuous variables. The entanglement of optical fields
produced by the first NOPA is successively enhanced by the second and the third
NOPAs from -5.3 to -8.1 below the quantum noise limit. The dependence
of the enhanced entanglement on the physical parameters of the NOPAs and the
reachable entanglement limitation for a given cascaded NOPA system are
calculated. The calculation results are in good agreement with the experimental
measurements.Comment: 5 pages, 4 figure
Numerical analysis of flexural performances of composite steel-timber beams under fire conditions
Recently, a novel type of composite structure, composite steel-timber (CST) structure, has attracted much attention by combining steel and timber in an effective way to form composite structural components, which unitises the advantages of high strength and excellent ductility of steel and decent sustainability and fire resistance of timber. However, the existing research is lacking, especially in structural fire design and analysis. In this study, based on the sequentially coupled method, the commercial finite element software ABAQUS was used to numerically simulate the dynamic performances in the temperature field and the flexural behaviours in the displacement field for a typical CST beam with a steel element embedded within the Glulam and connected by adhesives and bolts under standard fire for two hours. In the numerical simulations, the temperature distributions within the CST beam were explored, and the flexural performances of the beam in the displacement field were examined. Through the comparative analysis, the temperature distributions in the embedded steel beam and the surrounding Glulam beam under one-hour standard fire verified the advantages of this type of CST beam in structural fire design. Specifically, under a 2-hour standard fire, the surrounding Glulam could still protect the embedded steel beam from sustaining too high temperatures, so as to retain most of its material properties and help maintain the bearing capacity of the whole structure and improve the refractory limit. Parametric studies on the fire resistance of the CST beam were also conducted by adjusting the bolt spacing and the protection thickness of the Glulam. The obtained results indicated that reducing the bolt spacing and the thickness of the Glulam protection layer would have an adverse effect on the temperature distributions in the embedded steel element to a large extent, and would eventually lead to its rapid heating and strength loss and the final failure of the whole CST structure
Mining Unfollow Behavior in Large-Scale Online Social Networks via Spatial-Temporal Interaction
Online Social Networks (OSNs) evolve through two pervasive behaviors: follow
and unfollow, which respectively signify relationship creation and relationship
dissolution. Researches on social network evolution mainly focus on the follow
behavior, while the unfollow behavior has largely been ignored. Mining unfollow
behavior is challenging because user's decision on unfollow is not only
affected by the simple combination of user's attributes like informativeness
and reciprocity, but also affected by the complex interaction among them.
Meanwhile, prior datasets seldom contain sufficient records for inferring such
complex interaction. To address these issues, we first construct a large-scale
real-world Weibo dataset, which records detailed post content and relationship
dynamics of 1.8 million Chinese users. Next, we define user's attributes as two
categories: spatial attributes (e.g., social role of user) and temporal
attributes (e.g., post content of user). Leveraging the constructed dataset, we
systematically study how the interaction effects between user's spatial and
temporal attributes contribute to the unfollow behavior. Afterwards, we propose
a novel unified model with heterogeneous information (UMHI) for unfollow
prediction. Specifically, our UMHI model: 1) captures user's spatial attributes
through social network structure; 2) infers user's temporal attributes through
user-posted content and unfollow history; and 3) models the interaction between
spatial and temporal attributes by the nonlinear MLP layers. Comprehensive
evaluations on the constructed dataset demonstrate that the proposed UMHI model
outperforms baseline methods by 16.44% on average in terms of precision. In
addition, factor analyses verify that both spatial attributes and temporal
attributes are essential for mining unfollow behavior.Comment: 8 pages, 7 figures, Accepted by AAAI 202
Architectural formation of growable light steel structure and its 3D visualisation design and construction method
With the applications of new construction technologies and design ideas, innovative construction methods and architectural designs promote overall productivity and enrich architectural impressions. However, faced with the contradictions between construction efficiency, project benefits, and sustainability, together with the dynamically variable social demands and monotonous design of current temporary light steel structures, a new type of growable light steel structure with parameterisable and assembled architectural units is proposed. Besides, a fast-assembled track foundation that can be detachable and recycled is adopted. Both can promote the growth of light steel units. To be specific, its architectural spaces can be extended and contracted, and the structural form and service space can be adjusted by the reorganisation and optimisation of unit arrangements. Meanwhile, due to the advantages of information integrations and 3D visualisations of BIM technology, a BIM-based design and construction method of growable light steel structures is studied. Based on the arrangements of track and parametrically transformed light steel units, this study expands the architectural forms of light steel structures. It explores their respective applications in practical architectural design to solve current shortages of land resources, properly respond to variable building environments, simultaneously enrich the design schemes of current light steel structures, improve the utilisation rate of structural spaces, and enhance the aesthetic sensations of buildings
Small-Sample Inferred Adaptive Recoding for Batched Network Coding
Batched network coding is a low-complexity network coding solution to
feedbackless multi-hop wireless packet network transmission with packet loss.
The data to be transmitted is encoded into batches where each of which consists
of a few coded packets. Unlike the traditional forwarding strategy, the
intermediate network nodes have to perform recoding, which generates recoded
packets by network coding operations restricted within the same batch. Adaptive
recoding is a technique to adapt the fluctuation of packet loss by optimizing
the number of recoded packets per batch to enhance the throughput. The input
rank distribution, which is a piece of information regarding the batches
arriving at the node, is required to apply adaptive recoding. However, this
distribution is not known in advance in practice as the incoming link's channel
condition may change from time to time. On the other hand, to fully utilize the
potential of adaptive recoding, we need to have a good estimation of this
distribution. In other words, we need to guess this distribution from a few
samples so that we can apply adaptive recoding as soon as possible. In this
paper, we propose a distributionally robust optimization for adaptive recoding
with a small-sample inferred prediction of the input rank distribution. We
develop an algorithm to efficiently solve this optimization with the support of
theoretical guarantees that our optimization's performance would constitute as
a confidence lower bound of the optimal throughput with high probability.Comment: 7 pages, 2 figures, accepted in ISIT-21, appendix adde
Experimental realization of three-color entanglement at optical fiber communication and atomic storage wavelengths
Multi-color entangled states of light including low-loss optical fiber
transmission and atomic resonance frequencies are essential resources for
future quantum information network. We present the experimental achievement on
the three-color entanglement generation at 852 nm, 1550 nm and 1440 nm
wavelengths for optical continuous variables. The entanglement generation
system consists of two cascaded non-degenerated optical parametric oscillators
(NOPOs). The flexible selectivity of nonlinear crystals in the two NOPOs and
the tunable property of NOPO provide large freedom for the frequency selection
of three entangled optical beams, so the present system is possible to be
developed as practical devices used for quantum information networks with
atomic storage units and long fiber transmission lines.Comment: 4pages, 4 figure
Effect of the stroke-to-bore ratio on the performance of a dual-piston free piston engine generator
The free piston engine generator (FPEG) is considered as one of the next generation efficient energy conversion device because of its compact structure, high geometric power ratio and low pollution. This paper investigated the effect of stroke-to-bore (S/B) ratio on the system operation characteristics and engine performance, constructed a detailed numerical model in MATLAB/Simulink and verified the experimental data whose difference value could be controlled within 5%. The effect of five S/B ratios (0.84, 0.91, 0.99, 1.07 and 1.14) and three compression ratios (8, 9 and 10) was analysed at a constant bore diameter. The simulation results indicated that the operation frequency increased from 28.2 Hz to 48.3 Hz when the S/B ratio decreased from 1.14 to 0.84. The highest indicated power is 4.1 kW when the S/B ratio is 0.84 and the compression ratio (CR) is 10. While for high thermal efficiency and fuel economy design, larger S/B ratio and higher operating compression ratio should be selected while keeping the periodic energy input unchanged. The heat transfer loss decreased from 29.0% to 20.4% when the S/B ratio increased from 0.84 to 1.14. And in the long stroke, ignition position needs to lean back (from 6.8 mm to 24.8 when S/B increased from 0.84 to 1.14) so as to keep the compression ratio unchanged under different S/B ratios
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