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As the application of composite materials increases, analysis and optimum design for various dynamic loads as well as static loads are required. In this paper, we present an optimal design study using the equivalent static load method for laminated composite structures subjected to various nonlinear dynamic loads. First, the dynamic analysis of the laminate composite structure was performed using the finite element method. Next, the equivalent static load at each time step was calculated using the calculated dynamic response, and the static response optimization of the composite structure was performed by applying the calculated equivalent static load as a multi-load condition. Then, optimal design was performed by minimizing mass or maximizing strength by designing stacking thickness and stacking angle as design variables by applying various dynamic loads for the three different composite material structures. As a result of the optimization, the results of the conventional dynamic response optimization method, the error of less than 0.1 %, and the convergence speed up to 18 times were shown, and it was verified that the convergence speed was excellent while ensuring the accuracy of the solution. [ABSTRACT FROM AUTHOR]

Context-aware recommender systems (CARS) exploit multiple contexts to improve user experience in embracing new information and services. Tensor factorization (TF), a type of latent factor model, has achieved remarkable performance in CARS. TF learns latent representations of contexts by decomposing an observed rating tensor and combines the latent representations as a vector form to represent contextual influence on users and items. However, due to the limitation of the contextual expression power, they have difficulties in effectively capturing complex correlations among multiple contexts, and also the meaning of each context is diluted. To address the issue, we propose a reliable TF-based recommender system based on a proposed context tensor (CT-CARS), which incorporates a variety of correlations among contexts. CT-CARS contains a novel recommendation rating function and a learning algorithm. Specifically, the proposed context tensor elaborately captures the influences of both individual contexts and context combinations. Moreover, we introduce a novel parameter initialization based on past-learned results to improve the reliability of recommendations. The overall time complexity of our parameter learning algorithm grows linearly as dataset size increases. Experiments on six real-world datasets including two large-scaled datasets show that CT-CARS outperforms the existing state-of-the-art models in terms of both accuracy and reliability. [ABSTRACT FROM AUTHOR]

Background: The self-expandable metallic stent (SEMS) has been widely used for unresectable malignant biliary obstruction but eventually becomes occluded by tumor ingrowth/overgrowth and sludge. Therefore, we aimed to determine the therapeutic effectiveness of secondary stents and to find differences according to various combinations of the first and second stents for the management of occluded SEMSs in patients with malignant distal biliary obstruction. Methods: Between 1999 and November 2008, 77 patients with malignant biliary obstruction underwent secondary biliary stent placement as 'stent-in-stent' at three university hospitals in Korea (40 covered, 26 uncovered, and 11 plastic stents). The membrane of the covered SEMS was regarded as the barrier against tumor ingrowth. We categorized the patients into three groups based on whether the covered SEMS was either the first or the second stent: membrane-SEMS (18 covered-covered; 9 covered-uncovered; 22 uncovered-covered SEMS), bare-SEMS (17 uncovered-uncovered SEMS), and plastic stent (3 covered-plastic; 8 uncovered-plastic). Results: The median patency of second stents was 138, 109, and 88 days (covered, uncovered, and plastic stents). The second covered SEMSs had a significantly longer patency than plastic stents ( p = 0.047). In a multivariate analysis including membrane-SEMS, bare-SEMS, and plastic stent groups, the bare-SEMS had a worse cumulative stent patency (HR = 2.04, CI = 1.08-3.86) and survival time (HR = 2.37, CI = 1.25-4.49) than the membrane-SEMS. Patients with ampulla of Vater cancer had better stent patency (HR = 0.27, CI = 0.08-0.98) and survival (HR = 0.17, CI = 0.04-0.77) than those with other pancreatobiliary malignancies. In addition, antitumor treatment prolonged survival time (HR = 0.50, CI = 0.26-0.99). Conclusions: The placement of additional biliary stents using the 'stent-in-stent' method is an effective treatment for an occluded metallic primary stent. In addition, double biliary SEMS placement using at least one covered SEMS (in the primary and/or secondary procedure) might provide longer cumulative stent patency and survival than using uncovered SEMSs in both procedures. [ABSTRACT FROM AUTHOR]