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Fretting in the partial-slip and gross-slip regimes under a constant normal load is considered. The tangential force—displacement relations for the forward and backward motions are described based the generalized Cattaneo—Mindlin theory of tangential contact and Masing’s hypothesis on modelling the force—displacement hysteretic loop. Besides the critical force and displacement parameters (characterizing the triggering of sliding), the model includes one dimensionless fitting parameter that tunes the tangential contact stiffness of the friction—contact interface. Explicit expressions are derived for the main tribological parameters of the fretting loop, including the slip index and the signal index. |
Lidstone boundary value problems appear as a mathematical model of real world problems such as the study of bending of simply supported beams or suspended bridges [4–6]. The existence of positive solutions of the boundary value problems (BVPs) has created a great deal of interest due to wide applicability in both theory and applications [7, 8]. Some authors in the literature have obtained existence results about the solutions, positive solutions, or symmetric positive solutions of Lidstone type BVPs associated with ordinary differential equations, differential equations, and dynamic equations on time scales by using various methods (see [7–24] and the references therein). |
Coronavirus disease (COVID-19) is rapidly spreading worldwide. Recent studies show that radiological images contain accurate data for detecting the coronavirus. This paper proposes a pre-trained convolutional neural network (VGG16) with Capsule Neural Networks (CapsNet) to detect COVID-19 with unbalanced data sets. The CapsNet is proposed due to its ability to define features such as perspective, orientation, and size. Synthetic Minority Over-sampling Technique (SMOTE) was employed to ensure that new samples were generated close to the sample center, avoiding the production of outliers or changes in data distribution. |
Recently, virtual reality (VR) technology has been widely used in medical, military, manufacturing, entertainment, and other fields. These applications must simulate different complex material surfaces, various dynamic objects, and complex physical phenomena, increasing the complexity of VR scenes. Current computing devices cannot efficiently render these complex scenes in real time, and delayed rendering makes the content observed by the user inconsistent with the user’s interaction, causing discomfort. Foveated rendering is a promising technique that can accelerate rendering. |
Many studies showed that marrying younger is associated with a higher risk of divorce. We investigate the causal effect of marrying at an earlier age on women’s divorce risk. We exploit the introduction of the 1981 reform in China, which facilitated legal marriage for urban women younger than 25 years old, using the Chinese Census data. We show that the reform generated a kink in the mean age at marriage for women, which we use in a fuzzy regression kink design (RKD) to assess the causal effect of marrying younger on the probability of divorce. First, we confirm in our data the existence of a negative (in fact, a U-shaped) association between age at marriage and divorce, as commonly observed in previous studies from the USA. |
We study (nonconvex) quadratic optimization problems with complementarity constraints, establishing an exact completely positive reformulation under—apparently new—mild conditions involving only the constraints, not the objective. Moreover, we also give the conditions for strong conic duality between the obtained completely positive problem and its dual. Our approach is based on purely continuous models which avoid any branching or use of large constants in implementation. |
Depth sensors of low-cost acquisition devices (e.g. Microsoft Kinect, Asus Xtion) are coming into widespread use; however, 3D acquired data are generally large, heterogeneous, and complex to analyse and interpret. In this context, our overall goal is the analysis of the action of a subject in a 3D video, e.g. the action of a human or the movement of its subparts. To this end, the action classification is achieved through the analysis of the temporal variation of geometric (e.g. centroid path, volume variation, activated voxels) and kinematic (e.g. speed) properties in consecutive frames. Then, these descriptors and the corresponding histograms are used to search a frame in a 3D video and to compare 3D videos. |
We derive an adaptation of Li and Yau estimates for positive solutions of semilinear heat equations on Riemannian manifolds with nonnegative Ricci tensor. We then apply these estimates to obtain a Harnack inequality and to discuss monotonicity, convexity, decay estimates and triviality of ancient and eternal solutions. |
Principles of Marketing is designed to meet the scope and sequence for a one-semester marketing course for undergraduate business majors and minors. Principles of Marketing provides a solid grounding in the core concepts and frameworks of marketing theory and analysis so that business students interested in a major or minor in marketing will also be prepared for more rigorous, upper-level elective courses. Concepts are further reinforced through detailed, diverse, and realistic company and organization scenarios and examples from various industries and geographical locations. To illuminate the meaningful applications and implications of marketing ideas, the book incorporates a modern approach providing connections between topics, solutions, and real-world problems. Principles of Mar... |
This handbook describes the United States (U.S.) aviation weather program, products, and services. It also documents weather theory and its application to aviation. The objective of this handbook is to help the pilot and operator understand the basics of weather, aviation weather hazards, and aviation weather products. The information included is not prescriptive. Furthermore, the guidance and recommendations in this handbook are not legally binding in their own right and will not be relied upon by the FAA as a separate basis for affirmative enforcement action or other administrative penalty. Conformity with the guidance and recommendations is voluntary only and nonconformity will not affect rights and obligations under existing statutes and regulations. |
