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  • 1
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    Training Classifiers under Covariate Shift by Constructing the Maximum Consistent Distribution Subset (2015)
    Hindawi
    Details
    Publication Date: 2015-12-10
    Description: The assumption that the training and testing samples are drawn from the same distribution is violated under covariate shift setting, and most algorithms for the covariate shift setting try to first estimate distributions and then reweight samples based on the distributions estimated. Due to the difficulty of estimating a correct distribution, previous methods can not get good classification performance. In this paper, we firstly present two types of covariate shift problems. Rather than estimating the distributions, we then desire an effective method to select a maximum subset following the target testing distribution based on feature space split from the auxiliary set or the target training set. Finally, we prove that our subset selection method can consistently deal with both scenarios of covariate shift. Experimental results demonstrate that training a classifier with the selected maximum subset exhibits good generalization ability and running efficiency over those of traditional methods under covariate shift setting.
    Print ISSN: 1024-123X
    Electronic ISSN: 1563-5147
    Topics: Mathematics , Technology
    Published by Hindawi
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  • 2
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    RI-MDS: Multidimensional Scaling Iterative Localization Algorithm Using RSSI in Wireless Sensor Networks (2015)
    Hindawi
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    Publication Date: 2015-11-02
    Description: To improve the feasibility and the convenience of localization methods for wireless sensor networks, a localization algorithm RI-MDS (RSSI-based iterative-multidimensional scaling) is proposed. The RI-MDS method is centralized and mainly focuses on improving localization accuracy. It collects RSSI vectors as ranging basis and combines the metric MDS method and the nonmetric MDS method to accomplish the relative localization. Then it uses the maximum likelihood method in affine transformation to transform the relative coordinates to absolute ones. Our method has no need for additional equipment on the WSN nodes. Simulation and field experiments show that the average localization error and the localization error ratio of the RI-MDS method are relatively lower and thus they are more feasible.
    Print ISSN: 1550-1329
    Electronic ISSN: 1550-1477
    Topics: Electrical Engineering, Measurement and Control Technology
    Published by Hindawi
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  • 3
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    Synthesis of Spatially Correlated Earthquake Ground Motions Based on Hilbert Transform (2018)
    Hindawi
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    Publication Date: 2018-03-06
    Description: A simplified method for synthesizing spatially correlated earthquake ground motions is developed based on Hilbert transform and a reference earthquake record. In this method, one reference earthquake record is treated as the original ground motion, based on a series of generated ground motions. This procedure uses the instantaneous amplitude and the instantaneous phase of the record obtained using Hilbert transform to achieve the nonstationarity of ground motion. To establish the coherency between generated ground motions, an incoherence model is employed to describe the relation between the instantaneous phase at the present station and the instantaneous phases at previous stations. This type of phase is defined as the instantaneous coherence phase. In addition, time lag is included in the instantaneous coherence phase to prescribe the wave passage effect. The proposed Hilbert-transform-based method is efficient and avoids cumbersome parameter estimations as well as other drawbacks involved in some traditional synthesizing methods. Applications of this method demonstrate that the generated ground motions are statistically analogous with the reference record.
    Print ISSN: 1687-5591
    Electronic ISSN: 1687-5605
    Topics: Computer Science , Technology
    Published by Hindawi
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  • 4
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    Study on the Rock Mass Caving and Surface Subsidence Mechanism Based on an In Situ Geological Investigation and Numerical Analysis (2018)
    Hindawi
    Details
    Publication Date: 2018-07-26
    Description: To deeply understand the mechanism of the rock mass caving and associated surface subsidence during sublevel caving mining, the Xiaowanggou iron mine was selected as an engineering project case study. The study area was analyzed by means of an in situ geological investigation and numerical simulation. First, a borehole television (BHTV) system and a GPS monitoring system were used to monitor the caving process of the roof rock mass and the development of the surface subsidence; the monitoring time was thirteen months. Then, a numerical simulation was used to analyze the damage evolution of the rock mass. Research shows the following: (1) in situ geological monitoring results indicate that the caving process of the roof rock mass presents intermittent characteristics, where slow caving and sudden caving are conducted alternatively and the arched-caving trend is more pronounced with continuous mining. The surface subsidence, horizontal displacement, and horizontal deformation of the hanging wall are higher than that of the footwall, and the subsidence center gradually deflects to the hanging wall in the late stage of the +45m sublevel mining. (2) Numerical simulation results indicate that the extension and penetration of the shear and tensile cracks along the joints and intact rock bridges are the main factors causing the rock mass caving and the existence of the stress arch and its evolution process is the fundamental reason for the intermittent caving of the rock mass. The rapid development of damage to the hanging wall (the damage angle reduced) is the main cause of the deflection of the subsidence center affected by joints and the mining size. (3) In the future of mining, large-scale subsidence will occur on the surface of the hanging wall.
    Print ISSN: 1024-123X
    Electronic ISSN: 1563-5147
    Topics: Mathematics , Technology
    Published by Hindawi
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  • 5
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    Training Classifiers under Covariate Shift by Constructing the Maximum Consistent Distribution Subset (2015)
    Hindawi
    Details
    Publication Date: 2015-01-01
    Description: The assumption that the training and testing samples are drawn from the same distribution is violated under covariate shift setting, and most algorithms for the covariate shift setting try to first estimate distributions and then reweight samples based on the distributions estimated. Due to the difficulty of estimating a correct distribution, previous methods can not get good classification performance. In this paper, we firstly present two types of covariate shift problems. Rather than estimating the distributions, we then desire an effective method to select a maximum subset following the target testing distribution based on feature space split from the auxiliary set or the target training set. Finally, we prove that our subset selection method can consistently deal with both scenarios of covariate shift. Experimental results demonstrate that training a classifier with the selected maximum subset exhibits good generalization ability and running efficiency over those of traditional methods under covariate shift setting.
    Print ISSN: 1024-123X
    Electronic ISSN: 1563-5147
    Topics: Mathematics , Technology
    Published by Hindawi
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  • 6
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    Research on the Complexity and Chaos Control about a Closed-Loop Supply Chain with Dual-Channel Recycling and Uncertain Consumer Perception (2018)
    Hindawi
    Details
    Publication Date: 2018-01-01
    Description: According to game theory, chaotic dynamics theory, and complexity based on the literature review about the pricing strategy and recycling channels of the closed-loop supply chain, on the background of the widespread hybrid recycling channels in Chinese electronic products market, this paper builds a closed-loop supply chain model with dual-channel recycling composed of one manufacturer and one third-party. We assume that the consumer perception towards the remanufacturing products is uncertain and limited. We carry on theoretical analysis of this model and perform numerical simulations from the perspective of entropy theory. Results show that a precipitous speed of recycling price adjustment of the manufacturer or the third-party will both lead the system into a chaotic state and cause the entropy of the system to increase. The system is sensitive to initial conditions in this chaotic condition. Focusing on the harmful effects of chaotic system, we introduce adjustment parameter to efficiently control the chaos. The results have a strong reference value to practical problems, so it has a great value in both theory and application.
    Print ISSN: 1076-2787
    Electronic ISSN: 1099-0526
    Topics: Computer Science , Mathematics
    Published by Hindawi
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  • 7
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    Joint 2D-DOA and Frequency Estimation for L-Shaped Array Using Iterative Least Squares Method (2012)
    Hindawi
    Details
    Publication Date: 2012-01-01
    Description: We introduce an iterative least squares method (ILS) for estimating the 2D-DOA and frequency based on L-shaped array. The ILS iteratively finds direction matrix and delay matrix, then 2D-DOA and frequency can be obtained by the least squares method. Without spectral peak searching and pairing, this algorithm works well and pairs the parameters automatically. Moreover, our algorithm has better performance than conventional ESPRIT algorithm and propagator method. The useful behavior of the proposed algorithm is verified by simulations.
    Print ISSN: 1687-5869
    Electronic ISSN: 1687-5877
    Topics: Electrical Engineering, Measurement and Control Technology
    Published by Hindawi
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  • 8
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    A New and Environmentally Friendly Route for Preparation of Carbon Microspheres from Wheat Straw (2013)
    Hindawi
    Details
    Publication Date: 2013-01-01
    Description: The reactions were performed to synthesize carbon materials using wheat straw powder as raw material. The wheat straw powder was first hydrolyzed at the absence of a catalyst at 190°C for 1 h, then the hydrolyzate solution was used as carbon source to prepare carbon materials via hydrothermal carbonization at 180°C in the absence of a catalyst for 8 h. The influence of solid-liquid-ratio of wheat straw to water on the morphology of the product was investigated. The samples were examined by a scanning electron microscope and Fourier transform infrared spectroscopy. The results show that the product was carbon microspheres with a large number of O–H, CHO, and other functional groups, and the diameters of carbon microspheres noticeably depended on the solid-liquid ratio. When the solid-liquid ratio was 1 : 60, the diameters of carbon microspheres were in the range of 100 to 300 nm when the solid-liquid ratio was 1 : 40, carbon microspheres with larger and more uniform diameters mostly about 250 nm were obtained, and when the solid-liquid-ratio was 1 : 20, there were more larger carbon microspheres with diameters about 800 nm in the product and the surface of these carbon microspheres is smoother, whereas; the uniformity of the product deteriorates.
    Print ISSN: 2356-6140
    Electronic ISSN: 1537-744X
    Topics: Natural Sciences in General
    Published by Hindawi
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  • 9
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    Convergence of a Generalized USOR Iterative Method for Augmented Systems (2013)
    Hindawi
    Details
    Publication Date: 2013-01-01
    Description: Zhang and Shang (2010) have presented the Uzawa-SOR (USOR) algorithm to solve augmented systems. In this paper, we establish a generalized Uzawa-SOR (GUSOR) method for solving augmented systems, which is the extension of the USOR method. We prove the convergence of the proposed method under suitable restrictions on the iteration parameters. Lastly, numerical experiments are carried out and experimental results show that our proposed method with appropriate parameters has faster convergence rate than the USOR method.
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    Electronic ISSN: 1563-5147
    Topics: Mathematics , Technology
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  • 10
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    Staffing to Maximize Profit for Call Centers with Impatient and Repeat-Calling Customers (2015)
    Hindawi
    Details
    Publication Date: 2015-01-01
    Description: Motivated by call center practice, we study the optimal staffing of many-server queues with impatient and repeat-calling customers. A call center is modeled as an M/M/s+M queue, which is developed to a behavioral queuing model in which customers come and go based on their satisfaction with waiting time. We explicitly take into account customer repeat behavior, which implies that satisfied customers might return and have an impact on the arrival rate. Optimality is defined as the number of agents that maximize revenues net of staffing costs, and we account for the characteristic that revenues are a direct function of staffing. Finally, we use numerical experiments to make certain comparisons with traditional models that do not consider customer repeat behavior. Furthermore, we indicate how managers might allocate staffing optimally with various customer behavior mechanisms.
    Print ISSN: 1024-123X
    Electronic ISSN: 1563-5147
    Topics: Mathematics , Technology
    Published by Hindawi
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