Towards Efficient Path Query on Social Network with Hybrid RDF Management

The scalability and exibility of Resource Description Framework(RDF) model make it ideally suited for representing online social networks(OSN). One basic operation in OSN is to find chains of relations,such as k-Hop friends. Property path query in SPARQL can express this type of operation, but its implementation suffers from performance problem considering the ever growing data size and complexity of OSN.In this paper, we present a main memory/disk based hybrid RDF data management framework for efficient property path query. In this hybrid framework, we realize an efficient in-memory algebra operator for property path query using graph traversal, and estimate the cost of this operator to cooperate with existing cost-based optimization. Experiments on benchmark and real dataset demonstrated that our approach can achieve a good tradeoff between data load expense and online query performance

Hybrid theoretical, experimental and numerical study of vibration and buckling of composite shells with scatter in elastic moduli

AbstractHybrid theoretical, experimental and numerical method is proposed for free vibration and buckling of composite shell with unavoidable scatter in elastic moduli. Based on the Goggin’s measurement techniques, the elastic moduli for material T300-QY8911 are measured, and a set of experimental points are obtained. The measurements of elastic moduli are quantified by either (1) the smallest ellipsoid and (2) the smallest four-dimensional uncertainty hyper-rectangle. Then uncertainty propagation in vibration and buckling problems of composite shell by ellipsoidal analysis and interval analysis are, respectively, studied from the theoretical standpoint. Comparison between these analyses is performed numerically

Effect of different MIT rainfall event division methods on volume capture ratio of annual rainfall based on bioretention assessment

Volume capture ratio of annual rainfall (VCRAR) is the key parameter of low-impact development (LID) facilities design, which is significantly affected by the rainfall event division method. However, there is no universal agreement on how to determine an optimal division method to achieve it. A modified minimum inter-event time (MIT) method based on MATLAB software was proposed to find an optimal MIT value. The result showed that the optimal MIT value in Beijing is 200 min based on the daily rainfall data from 1987 to 2016, and the annual average rainfall events were 34.2 with an average rainfall depth of 13.7 mm. Taking bioretention facilities as an example, the errors of design VCRAR under different MIT values were compared based on a Stormwater Management Model (SWMM). The results showed that when design VCRAR was ≤50, 55–60, 60–75, 75–80 and >80%, the optimal MIT value for LID facilities design was 60, 120, 200, 360 and 1,440 min, respectively. Therefore, the optimal MIT should be flexibly selected with the changing of design VCRAR, to ensure that LID facilities meet the design goals. HIGHLIGHTS Combining the MIT with threshold statistical methods based on MATLAB software to obtain an optimal MIT value.; Comparing the effect of different MIT values on the design VCRAR based on SWMM.; RER, ERD and MERDR were analyzed under different MIT values.; The different optimal MIT values of different design VCRARs were obtained in Beijing.