#### Table of Content

20 December 2015, Volume 20 Issue 6

Research article
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Research article
 Compliant Assembly Modeling and Deformation Analysis Considering Macro Residual Stress in Engineering Component Li-na ZHANG, Hua WANG, Shu-hui LI 2015, 20 (6):  641-648.  doi: 10.1007/s12204-015-1671-2 Abstract ( 181 )   HTML ( 567 )   Based on the manufacturing history chain, a component’s macro residual stress is introduced to the subsequent assembly model. In the simulated method, the simulation cost is saved via mapping the bulk stress profile directly to the component compared to our previous study. It thus facilitates the finite element analysis (FEA) which takes the component location in blank and the thickness of blank as two influence parameters. The methodology is proved to be feasible by the validation experiment designed for a typical assembly structure from the aerospace industry. The results show that the bulk stress originating from material preparation affects the downstream large-scale assembly deformation. The investigation of this research helps systematically to improve compliant assembly precision.
 A Wireless Video Capsule Endoscopy System: Design and Realization Bing-quan ZHU, Guo-zheng YAN, Gang LIU, Wen-ming XU 2015, 20 (6):  649-653.  doi: 10.1007/s12204-015-1672-1 Abstract ( 197 )   HTML ( 358 )   Wireless capsule endoscopy (CE), an image inspection technique, has been an important advancement in the diagnosis of gastrointestinal (GI) tract diseases. A video capsule endoscopy (VCE) system is analyzed in this study. A complementary metal oxide semiconductor (CMOS) analog image sensor is adopted, and other illumination, communication and energy modules are designed for functional realization. Measuring only $?$11 mm×25 mm, the VCE has a total power consumption of 52.5 mW, which enables it to work continuously for 8 h. The in vivo experiment on a living pig indicates that a clear video with high frame rate of 30 f/s can be obtained.
 Price-Based Power Control Algorithm in Cognitive Radio Networks Based on Monotone Optimization Zheng-qiang WANG, Ling-ge2 JIANG, Chen HE 2015, 20 (6):  654-659.  doi: 10.1007/s12204-015-1673-0 Abstract ( 187 )   HTML ( 494 )   This paper considers a price-based power control problem in the cognitive radio networks (CRNs). The primary user (PU) can admit secondary users (SUs) to access if their interference powers are all under the interference power constraint. In order to access the spectrum, the SUs need to pay for their interference power. The PU first decides the price for each SU to maximize its revenue. Then, each SU controls its transmit power to maximize its revenue based on a non-cooperative game. The interaction between the PU and the SUs is modeled as a Stackelberg game. Using the backward induction, a revenue function of the PU is expressed as a non-convex function of the transmit power of the SUs. To find the optimal price for the PU, we rewrite the revenue maximization problem of the PU as a monotone optimization by variable substitution. Based on the monotone optimization, a novel price-based power control algorithm is proposed. Simulation results show the convergence and the effectiveness of the proposed algorithm compared to the non-uniform pricing algorithm.
 A Generalized Two-Level Bregman Method with Dictionary Updating for Non-Convex Magnetic Resonance Imaging Reconstruction Ming-hui ZHANG, Xiao-yang HE, Shen-yuan DU, Qie-gen* LIU 2015, 20 (6):  660-669.  doi: 10.1007/s12204-015-1674-z Abstract ( 180 )   HTML ( 147 )   In recent years, it has shown that a generalized thresholding algorithm is useful for inverse problems with sparsity constraints. The generalized thresholding minimizes the non-convex $p$-norm based function with $p<1$, and it penalizes small coefficients over a wider range meanwhile applies less bias to the larger coefficients. In this work, on the basis of two-level Bregman method with dictionary updating (TBMDU), we use the modified thresholding to minimize the non-convex function and propose the generalized TBMDU (GTBMDU) algorithm. The experimental results on magnetic resonance (MR) image simulations and real MR data, under a variety of sampling trajectories and acceleration factors, consistently demonstrate that the proposed algorithm can efficiently reconstruct the MR images and present advantages over the previous soft thresholding approaches.
 Numerical Simulation of Drawdown and Land Deformation in Pumping-Recovery Tests Performed on a Circular Excavation Kai-yong HUANG, Xiang-lian ZHOU, Jian-hua WANG 2015, 20 (6):  690-695.  doi: 10.1007/s12204-015-1678-8 Abstract ( 155 )   HTML ( 146 )   A mathematical model, which not only fully couples fluid flow and solid skeleton deformation in unsaturated porous elastic media but also considers deformable diaphragm walls, is formulated in axially symmetric cylindrical coordinates for drawdown and land deformation. Based on this model, pumping-recovery tests in various conditions are numerically simulated to reveal the effects of elastic modulus of soil $E$ and initial saturated hydraulic conductivity $K_{\rm sat0}$ on hydraulic head and land deformation. The heterogeneity with respect to $E$ and $K_{\rm sat0}$ is separately taken into account. Large elastic modulus of soil contributes to both dewatering process and deformation control. Either large or small initial saturated hydraulic conductivity may cause relatively high groundwater table, while the larger one leads to smaller displacements.
 Application of Back Analysis on Laterally Loaded Single Pile Feng WU, Jing-hai GONG, Kun FU 2015, 20 (6):  696-702.  doi: 10.1007/s12204-015-1679-7 Abstract ( 185 )   HTML ( 178 )   In views of the limitations of the existing methods for calculating the pile foundation capacity, a back analysis approach of the $m$-value is introduced. In order to consider the sensitivity of pile behavior to the $m$-value, the relationships between the applied horizontal loads at pile head and the corresponding $m$-value along with the pile stiffness changes are studied. Based on statistics data from the extensive in-situ tests, the back analysis results suggest an exponential expression for the $m$-value in various soil conditions and horizontal displacements at pile head. This method is capable of providing an accurate $m$-value in calculating the pile responses under lateral loads.
 Free Vibration Analysis of Cylindrical and Rectangular Sandwich Panels with a Functionally Graded Core Hua-dong LI, Xi ZHU, Zhi-yuan MEI, Ying-jun ZHANG 2015, 20 (6):  735-742.  doi: 10.1007/s12204-015-1684-x Abstract ( 174 )   HTML ( 110 )   Based on the Reissner assumptions, the free vibration analysis of simply supported cylindrical and rectangular sandwich panels with isotropic face sheets and a functionally graded core is concerned. Firstly, the expressions of the displacements, stresses and internal forces are presented according to the constitutive relations and stress states of the core and face sheets. Then, the dynamic stability and compatibility equations are given for cylindrical sandwich panels with functionally graded core, elastic modulus and density in which vary continuously in the thickness direction. Finally, the proposed solutions are validated by comparing the results of degenerate example with classical solutions, and a numerical analysis is performed on the example of simply supported cylindrical and rectangular sandwich panels. The elastic modulus and density of the functionally graded core are assumed to be graded by a power law distribution of volume fractions of the constituents, and the Poisson ratio is held constant. The effects of the distribution of functionally graded core's properties, the thickness-side ratios and ratio of radius $(R)$ to length $(l)$ $\kappa =R/l$ are also examined.