717 research outputs found
Model predictive control guidance for constrained mars pinpoint landing
No full textIn order to achieve pinpoint landing under various constraints during powered descent phase of landing on Mars, model predictive control (MPC) is employed in this paper by designing a novel performance index. Its main advantage is that it can ensure the pinpoint landing with online calculation and handle constraints as well, both of which are important in practical engineering missions. Detailed derivational process is given. Simulation results show the effectiveness of the proposed guidance
New Look-Angle Tracking Guidance Strategy for Impact Time and Angle Control
No full textThis paper presents a new guidance strategy for a certain class of homing missiles subject to various terminal constraints and lateral acceleration limit. To achieve zero miss distance in the presence of various terminal impact constraints, a planar engagement scenario of missiles is considered to develop a feedback guidance law of tracking a time-varying look angle that is modeled as an inverse tangent function. The proposed strategy can be applied to both the impact time control and the impact time and angle control guidance problems. Furthermore, it does not require any forms of time-to-go estimation, numerical iterations, and linearization procedures. Numerical simulations are conducted to validate the effectiveness, robustness, and energy efficiency of the proposed guidance strategy in comparison with other existing guidance strategies.
Learning From Multi-Perception Features for Real-Word Image Super-Resolution
No full textActual image super-resolution is an extremely challenging task due to complex degradations existing in the image. To solve this problem, two dominant methodologies have emerged: degradation-estimation-based Addressing actual image super-resolution remains a formidable challenge due to the intricate degradations present in images. Two primary methodologies have emerged: degradation-estimation-based and blind-based methods. The former often struggle to accurately estimate degradation, limiting their effectiveness on real low-resolution images. Conversely, blind-based methods rely on a single perceptual perspective, constraining their adaptability to diverse perceptual characteristics. In response to these challenges, we present MPF-Net, a novel super-resolution approach aimed at enhancing real-world image super-resolution tasks by enabling the model to learn multiple perceptual features from input images. Our method features a Multi-Perception Feature Extraction module (MPFE) designed to extract diverse perceptual details, complemented by Cross-Perception Blocks (CPB) facilitating the fusion of this information for efficient super-resolution reconstruction. Additionally, we introduce a contrastive regularization term (CR) to enhance the model's learning by leveraging newly generated HR and LR images as positive and negative samples. Experimental results on challenging real-world SR datasets demonstrate the superiority of our approach over existing state-of-the-art methods, both qualitatively and quantitatively.
Biomolecular condensates mediate bending and scission of endosome membranes
No full textAbstract Multivesicular bodies are key endosomal compartments implicated in cellular quality control through their degradation of membrane-bound cargo proteins 1–3 . The ATP-consuming ESCRT protein machinery mediates the capture and engulfment of membrane-bound cargo proteins through invagination and scission of multivesicular-body membranes to form intraluminal vesicles 4,5 . Here we report that the plant ESCRT component FREE1 6 forms liquid-like condensates that associate with membranes to drive intraluminal vesicle formation. We use a minimal physical model, reconstitution experiments and in silico simulations to identify the dynamics of this process and describe intermediate morphologies of nascent intraluminal vesicles. Furthermore, we find that condensate-wetting-induced line tension forces and membrane asymmetries are sufficient to mediate scission of the membrane neck without the ESCRT protein machinery or ATP consumption. Genetic manipulation of the ESCRT pathway in several eukaryotes provides additional evidence for condensate-mediated membrane scission in vivo. We find that the interplay between condensate and machinery-mediated scission mechanisms is indispensable for osmotic stress tolerance in plants. We propose that condensate-mediated scission represents a previously undescribed scission mechanism that depends on the physicomolecular properties of the condensate and is involved in a range of trafficking processes. More generally, FREE1 condensate-mediated membrane scission in multivesicular-body biogenesis highlights the fundamental role of wetting in intracellular dynamics and organization
Gendering the Planchette: Female Writer Qian Xi's (1872–1930) Spiritual World
No full textAbstract
Fuji (wielding the planchette, or spirit writing) was in vogue among Ming-Qing literati, and its influence extended into modern times. Existing studies focus on this popular divination itself or on men's writings related to this practice. This article, instead, explores the poetry and prose of a female writer, Qian Xi, and her writing activities associated with this divination. Qian claims that the spirits she communicated with include several female immortals and her deceased husband. Some of the questions the author explores are: What are the characteristics of Qian's writings? What inspired Qian to participate in spirit writing? What role did this practice play in Qian's life and writing? Regarding the emotions, thoughts, and works of Qian, what types of information can spirit writing and corresponding poetic and prosaic compositions provide? Instead of simplifying and disregarding the ritual of wielding the planchette as bizarre, superstitious, or even mad, the author argues that it played a meaningful role in shaping Qian's literary images and enhancing her literary productivity. More important, Qian Xi's strategies of using spirit writing to stimulate her literary creations was significant in meeting her emotional needs, highlighting her identity as a talented woman, and demonstrating the worth of her very existence.</jats:p
Preventing Chronic Disease (PCD)
No full textIntroductionWomen veterans are a fast-growing segment of the veteran population, yet they face many barriers to medical care. The objective of this study was to examine factors that put women veterans at risk for a financial barrier to medical care.MethodsWe conducted repeated cross-sectional analyses of data from the 2003, 2004, 2009, and 2010 Behavioral Risk Factor Surveillance System. We used weighted logistic regression to examine the risk of a financial barrier to medical care as the primary outcome in a multivariate model controlling for factors in health-related domains.ResultsIn 2010, there were an estimated 1,719,750 (11.6%) working-aged veterans who needed to see a doctor in the previous 12 months but could not because of cost. For women, 13.4% faced this financial barrier. Over the study period, facing a financial barrier was consistently associated with insurance coverage, physical and mental distress days, and having children in the home. Other associations emerged in particular years, such as binge drinking in 2010. The trends for women veterans relative to men and for younger women veterans relative to older women veterans show reduction in financial barriers to health care.ConclusionThe Veteran\u2019s Health Administration (VHA) should continue efforts to reduce financial and other barriers, especially among the higher risk groups we identified. This will help meet the VHA\u2019s objectives of providing comprehensive care to all veterans including women
Scalable Learning with Privacy Over Graphs
No full textGraphs have well-documented merits for modeling complex systems, including financial, biological, and social networks. Network nodes can also include attributes such as age or gender of users in a social network. However, the size of real-world networks can be massive, and nodal attributes can be unavailable. Moreover, new nodes may emerge over time, and their attributes must be inferred in real time. In this context, the present paper deals with scalable learning of nodal attributes by estimating a nodal function based on noisy observations at a subset of nodes. A multikernel-based approach is developed which is scalable to large-size networks. The novel method is capable of providing real-time evaluation of the function values on newly-joining nodes without resorting to a batch solver. In addition, the novel scheme only relies on an encrypted version of each node's connectivity, which promotes privacy. Experiments on real datasets corroborate the effectiveness of the proposed methods.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Signal Processing System
Take a prior from other tasks for severe blur removal
No full textRecovering clear structures from severely blurry inputs is a huge challenge due to the detail loss and ambiguous semantics. Although segmentation maps can help deblur facial images, their effectiveness is limited in complex natural scenes because they ignore the detailed structures necessary for deblurring. Furthermore, direct segmentation of blurry images may introduce error propagation. To alleviate the semantic confusion and avoid error propagation, we propose utilizing high-level vision tasks, such as classification, to learn a comprehensive prior for severe blur removal. We propose a feature learning strategy based on knowledge distillation, which aims to learn the priors with global contexts and sharp local structures. To integrate the priors effectively, we propose a semantic prior embedding layer with multi -level aggregation and semantic attention. We validate our method on natural image deblurring benchmarks by introducing the priors to various models, including UNet and mainstream deblurring baselines, to demonstrate its effectiveness and generalization ability. The results show that our approach outperforms existing methods on severe blur removal with our plug -and -play semantic priors.
How Vertical Compression Triggers Lateral Interlayer Slide for Metallic Molybdenum Disulfide?
No full textThe isostructural phase transitions such as in compressed molybdenum disulfide -(MoS2) are ubiquitous in nature, but surprisingly, how and why the vertical compression driven lateral interlayer sliding are still open questions of interest. Here, we address the tribological determination of the pressure-driven interlayer sliding for the structural and electric tuning in compressed -MoS2 bilayer by using ab initio calculations. The density functional calculations demonstrate the pressure-driven evolution of interlayer potential energy landscape, providing the preferred sliding pathway for initiating mutual sliding of crystal faces between -MoS2 bilayers. Interestingly, even though the 2Ha stacking becomes more stable than the 2Hc stacking at a load of about 9.2 GPa, a spontaneous slippage would take place only around 30.1 GPa, when the sliding barrier of saddle stacking vanishes as a consequence of the load-driven modification of the potential energy surface. The structural transition from 2Hc-MoS2 to 2Ha-MoS2 is thus triggered, which allows for the semiconductor-metal transition of the bilayer under pressure. These results agree with recent experimental and dynamics observations of the transition occurring almost completely at 28-30 GPa in bulk crystals. By elucidating these criteria, we suggest that the study may be thus extended to understand the macroscopic properties of the bulk layered crystals such as the possible occurrence of phase transitions taking place at solid interfaces from the atomistic sliding mechanisms at the microscopic scale
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