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Most Web search diversity approaches can be categorized as Document Level Diversification ( DocLD ), Topic Level Diversification ( TopicLD ) or Term Level Diversification ( TermLD ). DocLD selects the relevant documents with minimal content overlap to each other. It does not take the coverage of query subtopics into account. TopicLD solves this by modeling query subtopics explicitly. However, the automatic mining of query subtopics is difficult. TermLD tries to cover as many query topic terms as possible, which reduces the task of finding a query's subtopics into finding a set of representative topic terms. In this paper, we propose a novel User Session Level Diversification ( UserLD ) approach based on the observation that a query's subtopics are implicitly reflected by the search intents in different user sessions. Our approach consists of two phases: (I) Session Graph Construction and (II) Diversity Reranking . For a given query, phase (I) builds a Session Graph which considers relevant user sessions and preliminary retrieval results as nodes and the nodes' pairwise similarities as edge weights. Phase (II) reranks the preliminary retrieval results by minimizing a Session Graph based diversity loss function. Extensive experiments on two standard datasets of NACSIS Test Collections for IR (NTCIR) demonstrate the effectiveness of our approach. The advantage of our approach lies in its ability of avoiding mining the query subtopics in advance while achieving almost the same or better performances compared with previous approaches. [ABSTRACT FROM AUTHOR]

Many parallel bridges have been recently designed and built around the world to accommodate the ever-increasing volumes of vehicle and rail traffic. Accordingly, the aerodynamic interference around the parallel girders becomes important to investigate for a more accurate estimation of wind-induced effects on bridges. In this study, a wide range of gap-width ratios (0–15) for parallel box girders are selected to investigate the aerodynamic interference using three-dimensional large eddy simulation at zero wind attack angle. Specific aerodynamic characteristics, including the flow structures, pressure distributions, mean values and standard deviations of the force coefficients, Strouhal number as well as spanwise correlations of the aerodynamic coefficients are examined with various gap-width ratios. The detailed comparison work demonstrates a good agreement with the experimental work. The simulation results reveal that all the aerodynamic characteristics are significantly influenced by the gap-width ratio. The three regions are bounded by critical gap-width ratios of G/B = 0.25 and G/B = 5. There are large changes in behavior at G/B = 0.25, whereas, for G/B > 5, interference effects are not evident. The interference effects on both mean and fluctuating aerodynamic coefficients of parallel box girders are also quantified and summarized. • A wide range of gap-width ratios(0–15) for parallel box girders is selected to investigate the aerodynamic interference using three-dimensional large eddy simulation. • The three regions are bounded by critical gap-width ratios of G/B = 0.25 and G/B = 5. There are large changes in behavior at G/B = 0.25, whereas for G/B > 5, interference effects are not evident.. • The aerodynamic interference factors for root mean square of fluctuating force coefficients are proposed to express the impact of aerodynamic interference effect. • The spanwise correlations of force coefficients suddenly increase at G/B = 0.25. [ABSTRACT FROM AUTHOR]

Ambient temperature changes may cause considerable and complicated global deformation in long-span bridges. This study investigates the mechanisms of temperature-induced mid-span vertical displacement of symmetrical twin-pylon cable-stayed bridges through geometric models. General formulas are presented to separately quantify the sensitivity of the concerned displacement with respect to the cable, girder, and pylon temperature variations. The applicability of the proposed formulas is verified using numerical models of 15 bridges. The subsequent parametric analysis reveals the relationships among the temperature sensitivity, material property (linear expansion coefficients), and structural geometries (main span L 0 , side-to-main span ratio γ 0 , pylon height-to-span ratio ξ , and pylon height ratio λ 0). Furthermore, the relative impacts of the temperature changes of different structural components are compared. This study focuses on the calculation of thermal deformation of a general category of cable-stayed bridges rather than a specific one. The formulas provided show the advantages of conceptual clarity, calculation simplicity, and general applicability. They also have far-reaching implications on the design of structural health monitoring systems and the establishment of the load–response baseline models. [ABSTRACT FROM AUTHOR]