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Now showing items 1 - 16 of 32

  • Reverse Spatial Visual Top-$k$ Query

    Zhu, Lei   Song, Jiayu   Yu, Weiren   Zhang, Chengyuan   Yu, Hao   Zhang, Zuping  

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  • A Delay-Aware and Reliable Data Aggregation for Cyber-Physical Sensing

    Zhang, Jinhuan   Long, Jun   Zhang, Chengyuan   Zhao, Guihu  

    Physical information sensed by various sensors in a cyber-physical system should be collected for further operation. In many applications, data aggregation should take reliability and delay into consideration. To address these problems, a novel Tiered Structure Routing-based Delay-Aware and Reliable Data Aggregation scheme named TSR-DARDA for spherical physical objects is proposed. By dividing the spherical network constructed by dispersed sensor nodes into circular tiers with specifically designed widths and cells, TSTR-DARDA tries to enable as many nodes as possible to transmit data simultaneously. In order to ensure transmission reliability, lost packets are retransmitted. Moreover, to minimize the latency while maintaining reliability for data collection, in-network aggregation and broadcast techniques are adopted to deal with the transmission between data collecting nodes in the outer layer and their parent data collecting nodes in the inner layer. Thus, the optimization problem is transformed to minimize the delay under reliability constraints by controlling the system parameters. To demonstrate the effectiveness of the proposed scheme, we have conducted extensive theoretical analysis and comparisons to evaluate the performance of TSR-DARDA. The analysis and simulations show that TSR-DARDA leads to lower delay with reliability satisfaction.
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  • Academic Activities Transaction Extraction Based on Deep Belief Network

    Wang, Xiangqian   Huang, Fang   Wan, Wencong   Zhang, Chengyuan  

    Extracting information about academic activity transactions from unstructured documents is a key problem in the analysis of academic behaviors of researchers. The academic activities transaction includes five elements: person, activities, objects, attributes, and time phrases. The traditional method of information extraction is to extract shallow text features and then to recognize advanced features from text with supervision. Since the information processing of different levels is completed in steps, the error generated from various steps will be accumulated and affect the accuracy of final results. However, because Deep Belief Network (DBN) model has the ability to automatically unsupervise learning of the advanced features from shallow text features, the model is employed to extract the academic activities transaction. In addition, we use character-based feature to describe the raw features of named entities of academic activity, so as to improve the accuracy of named entity recognition. In this paper, the accuracy of the academic activities extraction is compared by using character-based feature vector and word-based feature vector to express the text features, respectively, and with the traditional text information extraction based on Conditional Random Fields. The results show that DBN model is more effective for the extraction of academic activities transaction information.
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  • Inverted Linear Quadtree: Efficient Top K Spatial Keyword Search

    Zhang, Chengyuan   Zhang, Ying   Zhang, Wenjie   Lin, Xuemin  

    With advances in geo-positioning technologies and geo-location services, there are a rapidly growing amount of spatio-textual objects collected in many applications such as location based services and social networks, in which an object is described by its spatial location and a set of keywords (terms). Consequently, the study of spatial keyword search which explores both location and textual description of the objects has attracted great attention from the commercial organizations and research communities. In the paper, we study two fundamental problems in the spatial keyword queries: top k spatial keyword search (TOPK-SK), and batch top k spatial keyword search (BTOPK-SK). Given a set of spatio-textual objects, a query location and a set of query keywords, the TOPK-SK retrieves the closest k objects each of which contains all keywords in the query. BTOPK-SK is the batch processing of sets of TOPK-SK queries. Based on the inverted index and the linear quadtree, we propose a novel index structure, called inverted linear quadtree (IL-Quadtree), which is carefully designed to exploit both spatial and keyword based pruning techniques to effectively reduce the search space. An efficient algorithm is then developed to tackle top k spatial keyword search. To further enhance the filtering capability of the signature of linear quadtree, we propose a partition based method. In addition, to deal with BTOPK-SK, we design a new computing paradigm which partition the queries into groups based on both spatial proximity and the textual relevance between queries. We show that the IL-Quadtree technique can also efficiently support BTOPK-SK. Comprehensive experiments on real and synthetic data clearly demonstrate the efficiency of our methods.
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  • Does the Device Matter in Goal-Directed Fluid Therapy?

    Zhang, Chengyuan  

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  • Crossing generative adversarial networks for cross-view person re-identification

    Zhang, Chengyuan   Wu, Lin   Wang, Yang  

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  • What can we learn from the history of male anorexia nervosa?

    Zhang, Chengyuan  

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  • CNN-VWII: An efficient approach for large-scale video retrieval by image queries

    Zhang, Chengyuan   Lin, Yunwu   Zhu, Lei   Liu, Anfeng   Zhang, Zuping   Huang, Fang  

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  • DFTerNet: Towards 2-bit Dynamic Fusion Networks for Accurate Human Activity Recognition

    Yang, Zhan   Raymond, Osolo Ian   Zhang, Chengyuan   Wan, Ying   Long, Jun  

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  • Multiple-point statistical prediction on fracture networks at Yucca Mountain

    Liu, Xiaoyan   Zhang, Chengyuan   Liu, Quansheng   Birkholzer, Jens  

    In many underground nuclear waste repository systems, such as Yucca Mountain project, water flow rate and amount of water seepage into the waste emplacement drifts are mainly determined by hydrological properties of fracture network in the surrounding rock mass. Natural fracture network system is not easy to describe, especially with respect to its connectivity which is critically important for simulating the water flow field. In this paper, we introduced a new method for fracture network description and prediction, termed multi-point-statistics (MPS). The process of Multi-point Statistical method is to record multiple-point statistics concerning the connectivity patterns of fracture network from a known fracture map, and to reproduce multiple-scale training fracture patterns in a stochastic manner, implicitly and directly. It is applied to fracture data to study flow field behavior at Yucca Mountain waste repository system. First, MPS method is used to create fracture network with original fracture training image from Yucca Mountain dataset. After we adopt a harmonic and arithmetic average method to upscale the permeability to a coarse grid, THM simulation is carried out to study near-field water flow in surrounding rock of waste emplacement drifts. Our study shows that connectivity or pattern of fracture network can be grasped and reconstructed by Multi-Point-Statistical method. In theory, it will lead to better prediction of fracture system characteristics and flow behavior. Meanwhile, we can obtain variance from flow field, which gives us a way to quantify uncertainty of models even in complicated coupled THM simulation. It indicates that Multi-Point Statistics is a potential method to characterize and reconstruct natural fracture network in a fractured rock mass with advantages of quantifying connectivity of fracture system and its simulation uncertainty simultaneously.
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  • Detachment Characteristics of Deposited Particles in Porous Medium:Experimentation and Modeling

    Cui, Xianze   Liu, Quansheng   Zhang, Chengyuan  

    This paper presents an experimental study of particle transport in porous medium using a self-developed sand layer transportation-deposition testing system, aiming at delineating the detachment characteristics of deposited particles in porous medium. Two experimental modes, increase flow velocity and change flow direction, were adopted in this study. The tests were conducted using quartz powder as the particles and quartz sand as the porous media to study the response of detachment characteristics to changes in particle diameter (, with median diameter 18 and 41 m) and grain diameter (, with median diameter 0.36 and 1.25 mm). Breakthrough curves after the second peak were well described by a double exponential model with parameters of weight coefficient and detachment coefficient. This study shows that both modes can change the detach rate of deposited particles observably, and detach rate is affected by the value of flow velocity greatly.
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  • Physical factors affecting the transport and deposition of particles in saturated porous media

    Cui, Xianze   Liu, Quansheng   Zhang, Chengyuan  

    Saturated sand box experiments were conducted to explore the effect of various physical factors on the transport and deposition of suspended particles in porous media. Red quartz powder and natural quartz sand were employed in the study and acted as suspended particles and porous media, respectively. Particles were injected into the sand box in two modes, i.e., pulse injection and continuous injection. Tests were performed at various particle concentrations, flow velocities, deposition rate coefficient and longitudinal dispersion coefficient by both injection modes. The breakthrough curves were described with the analytical solution of a convection-dispersion equation, in which first-order deposition kinetics were taken into account. Different behavior of suspended-particle transport and deposition in porous media was observed under different injection modes and experimental conditions. The results show that effluent concentration was approximately linear with the initial particle concentration. The deposition rate coefficient depends strongly on particle size and flow velocity, and the transport and deposition process was very sensitive to it. Furthermore, the longitudinal dispersion coefficient increases with increasing flow rate, and particles are easier to transport through pores as the longitudinal dispersion coefficient increases. This study shows the importance of particle concentration, flow velocity, deposition rate coefficient and longitudinal dispersion coefficient in the transport and deposition process of suspended particles.
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  • PAC-GAN: An effective pose augmentation scheme for unsupervised cross-view person re-identification

    Zhang, Chengyuan   Zhu, Lei   Zhang, ShiChao   Yu, Weiren  

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  • AN ROCK-PHYSICS-BASED COMPLEX PORE-FLUID-DISTRIBUTION MODEL TO SEISMIC DYNAMICAL RESPONSE

    ZHANG, CHENGYUAN   LIU, XIAOYAN   XI, DAOYING   LIU, QUANSHENG  

    It is very important to know how the reservoir rock and its fluid properties are linked to seismic dynamic response. Literatures show that there are a variety of rock-physics models such as the most famous Biot-Gassmann equation aimed at the relationship between seismic velocity and liquid saturation. Most of these models make a fundamental assumption of one fluid phase or homogeneous phase within the pore volume. In this paper, we discuss possible seismic velocities change in a two immiscible pore fluids (i.e. water-gas) saturated reservoir with patchy saturation distribution. It is found that P-wave velocity of a reservoir rock with the same saturation but different pore fluid distribution exhibits noticeable variation and deviate overall from Gassmann's results. We use DEM theory to explain this phenomenon. It belongs to hybrid approach in rock-physics modeling and can handle complex pore-fluid-distribution cases. Based on the modeling study, we found that various fluid-distribution models may significantly affect the modulus and P-wave velocity. The seismic reflection time, amplitude and phase characteristics may change with the choice of pore-fluid-distribution models. Relevant rock mechanical experiments indicate the same trend of seismic responses. It also be proven by seismic reservoir monitoring experiment (time lapse study) that incorrect conclusion may be drawn about the strong seismic reflection in pure Utsira Sand if the microscopic pore-fluid-distribution effects are not taken into account.
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  • The correlation between common 2D femoral notch parameters and 3D notch volume: a retrospective MRI study

    Zhang, Chengyuan   Zhang, Xuancheng   Fang, Zhaoyi   Wang, Feng   Yuan, Feng   Xie, Guoming   Zhao, Jinzhong  

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  • Experimental investigation of suspended particles transport through porous media:particle and grain size effect

    Liu, Quansheng   Cui, Xianze   Zhang, Chengyuan   Huang, Shibing  

    Particle and grain size may influence the transportation and deposition characteristics of particles within pollutant transport and within granular filters that are typically used in wastewater treatment. We conducted two-dimensional sandbox experiments using quartz powder as the particles and quartz sand as the porous medium to study the response of transportation and deposition formation to changes in particle diameter (d(s), with median diameter 18, 41, and 82 mu m) and grain diameter (d(p), with median diameter 0.36, 1.25, and 2.82 mm) considering a wide range of diameter ratios (d(s)/d(p)) from 0.0064 to 0.228. Particles were suspended in deionized water, and quartz sand was used as the porous medium, which was meticulously cleaned to minimize any physicochemical and impurities effects that could result in indeterminate results. After the experiments, the particle concentration of the effluent and particle mass per gram of dry sands were measured to explore changes in transportation and deposition characteristics under different conditions. In addition, a micro-analysis was conducted to better analyse the results on a mesoscopic scale. The experimental observation analyses indicate that different diameter ratios (d(s)/d(p)) may lead to different deposit formations. As d(s)/d(p) increased, the deposit formation changed from 'Random Deposition Type' to 'Gradient Deposition Type', and eventually became 'Inlet Deposition Type'.
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