1,721,255 research outputs found
Development of a predictive model for severe peripartum hemorrhage in placenta accreta spectrum cases under neuraxial anesthesia
No full textThe data for development of a predictive model for severe peripartum hemorrhage in placenta accreta spectrum cases under neuraxial anesthesia
Vibration suppression of suspended cables with three-to-one internal resonances via time-delay feedback
Full text linkBased on the time-delay feedback control, the vibration suppression of suspended cables with three-to-one internal resonances are investigated. Initially, the nonlinear differential equation of motion for a suspended cable under time-delay feedback control is considered, and a discrete model is derived using the Galerkin method. Subsequently, the method of multiple scales is employed to perturbatively solve the discrete time-delay differential equation, determining the modulation equations around the first primary resonance. Steady-state and periodic solutions of the modulation equations are detected numerically. Numerical results indicate that the internal resonance enhances the nonlinear dynamical complexity of the controlled suspended cable. It is observed that the time delay and control gain affect the controlled system: in particular, an increase in control gain leads to a reduction in response amplitude. By adjusting the time delay and control gain, the critical excitation can be altered, an aspect that could be very useful from a practical point of view. This research sheds light on the intricate dynamics of suspended cable and provides a theoretical foundation for designing more effective control strategies in engineering applications
Time-delay feedback control of a suspended cable driven by subharmonic and superharmonic resonance
Full text linkThe longitudinal time-delay feedback control strategy is implemented to suppress the subharmonic and superharmonic responses of the suspended cable. Formulated based on the Hamilton variational principle and the longitudinal time-delay feedback strategy, the in -plane nonlinear differential equations for a suspended cable are formulated, and Galerkin method is utilized to transform the equations into delayed differential equations. By using the method of multiple scales, approximate solutions for the 1/2-subharmonic and second-order superharmonic resonance responses of the controlled suspended cable were derived. The effects of the time delay and control gain are obtained through numerical examples. The research results demonstrate that through the adjustment of control gain and time delay, resonance regions can be avoided, effectively suppressing large-amplitude vibrations in the suspended cable, thereby achieving favorable control performance
Spatial gene variation mechanism based on rural tourism for traditional villages in Southern Shanxi, China / Li Yanan
No full textRural tourism, owing to its significant economic benefits, has become an almost indispensable option for the development of traditional villages in China, particularly under the national policies of rural revitalization and poverty alleviation. The advantage of rural tourism in traditional villages lies in their spatial environment, which has been refined over time and embodies the wisdom of the local people. The charm of this spatial environment is rooted in the intergenerational inheritance of spatial genes. However, as an external factor, rural tourism inevitably impacts the spatial environment of traditional villages and affects the continuity of these spatial genes. Many problems induced by rural tourism such as spatial homogenization, decreasing number, and weakening of social ties in traditional villages have been confirmed by previous studies, making the spatial variation of traditional villages caused by rural tourism that must be studied. This study borrows the concept of spatial genes from human geography to explore how rural tourism, as an external factor, changes traditional villages' spatial genes. This thesis aims to establish a spatial variation mechanism framework for traditional villages due to rural tourism that will ensure the continuity of the spatial environment of traditional villages genetically. Because local villagers are the creators, users, and continuers of spatial genes, this study adopted a villager-centered mixed research methodology, including questionnaires, UAV observation, and semi-structured interviews. Finally, the spatial variation mechanism framework was developed through triangulation by comparing and validating questionnaires, UAV observations, and interview data. The research data of this study are based on four traditional villages in southern Shanxi, China. Initially, a questionnaire survey is conducted to validate 13 indicators of rural tourism'simpact on the spatial environment of traditional villages in economic, social, and cultural dimensions, and find out the effect parameters of each indicator. Subsequently, the spatial condition of the four traditional villages was acquired through UAV observation. Then semi-structured interviews probed the villagers' intrinsic motivations behind spatial changes. Finally, by comparing and verifying these three kinds of data through the triangulation method to identify the indicators of spatial variation in traditional villages and quantify their impact levels, alongside uncovering the intrinsic causes of such changes. This process elucidates the mechanism of spatial variation in traditional villages, thereby informing a villager-centered guidance framework for tourism development within traditional villages to ensure the continuity of spatial genes and contribute to the sustainable development of traditional villages based on rural tourism
High resolution, large area vision-based tactile sensing based on a novel piezoluminescent skin
No full textThe ability to precisely perceive external physical interactions would enable robots to interact effectively with the environment and humans. While vision-based tactile sensing has improved robotic grippers, it is challenging to realize high resolution vision-based tactile sensing in robot arms due to presence of curved surfaces, difficulty in uniform illumination, and large distance of sensing area from the cameras. In this article, we propose a novel piezoluminescent skin that transduces external applied pressures into changes in light intensity on the other side for viewing by a camera for pressure estimation. By engineering elastomer layers with specific optical properties and integrating a flexible electroluminescent panel as a light source, we develop a compact tactile sensing layer that resolves the layout issues in curved surfaces. We achieved multipoint pressure estimation over an expansive area of 502 cm
2 with high spatial resolution, a two-point discrimination distance of 3 mm horizontally and 5 mm vertically which is comparable to that of human fingers as well as a high localization accuracy (RMSE of 1.92 mm). These promising attributes make this tactile sensing technique suitable for use in robot arms and other applications requiring high resolution tactile information over a large area.</p
Social Influence from Personalized Recommendations to Trusting Beliefs of Websites: Intermediate Role of Social Presence
No full text
With the increasing prevalence of online shopping, many companies have added “personalized recommendation” modules on their websites to collect customers’ click-stream data in real time and conduct relevant analysis, which will both assist the decision-making of the web owners and enrich the interactive experience of the customers. A website with more personalized recommender system allows users to experience others as psychologically present being, conveys a feeling of human warmth and sociability which is believed critical for the formation of consumers’ trust towards online stores. In this study, a laboratory experiment was conducted to empirically examine the effects of the level of perceived personalization on consumers’ trusting beliefs towards online store. The result also demonstrated that the perception of social presence can partially mediate the effect of perceived personalization on consumer’s trusting beliefs. </p
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Force-dependent variable impedance controller for contact-rich tasks under reference trajectory uncertainty
No full textIn robotic manipulation, performing force-tracking tasks in an uncertain environment poses the risk of the robot and the environment encountering high contact forces. While learning control methods are used wheninteracting with uncertain environments, the robots generally take some time to learn the correct reference path in such scenarios. During this process, it is important to reduce the contact forces until the environment properties are learned to ensure the safety of the interaction. To this end, this article proposes a force-dependent variable impedance controller (FVIC) that provides compliance in the presence of reference uncertainty and improves the position tracking accuracy as the certainty of the reference position increases. In this FVIC, the stiffness and dampingof the robot are defined as functions of force and force rate, respectively, to ensure compliance and stability. The proposed method is validated via simulations and experiments conducted using the Kinova Gen3 7DOF robot. The results show that, unlike the traditional variable impedance control (VIC) methods, this method ensures stability without compromising the desired impedance characteristics. It is further demonstrated that with this method, the contact forces can be maintained significantly low when there’s a reference uncertainty, thus ensuring safety
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