1,386 research outputs found
Design and performance of polyurethane elastomers composed with different soft segments
Thermoplastic polyurethane elastomers (TPUs) are widely used in a variety of applications as a result of flexible and superior performance. However, few scholars pay close attention on the design and synthesis of TPUs through the selfâdetermined laboratory process, especially on definite of chemical structures and upon the influence on properties. To investigate the properties of synthesized modifier based on chemical structure, firstly each kind of unknown structure and composition ratio of TPUs was determined by using a new method. Furthermore, the thermal characteristics and mechanical properties of modifiers were exposed by thermal characteristics and mechanics performance tests. The experimental results indicate that TPUs for use as an asphalt modifier can successfully be synthesized with the aid of semiâprepolymer method. The linear backbone structure of TPUs with different hard segment contents were determined by micro test methods. The polyesterâbased TPUs had thermal behavior better than the polyether-based TPUs; conversely, the low temperature performance of polyetherâbased TPUs was superior. Most importantly, it was found that the relative molecular mass of TPUs exhibited a weak effect on the mechanical properties, whereas the crystallinity of hard segment showed a significant influence on the properties of TPUs
Analytical Frequency Nadir Prediction Considering Inverter-Based Fast Frequency Response
This letter develops an analytical frequency nadir prediction method that
allows for the consideration of three potential forms of fast frequency
response (FFR) provided by inverter-based resources. The proposed method
provides fast and accurate frequency nadir estimation after N-1 generation
tripping contingencies. Our method is grounded on the closed-form solution for
the frequency nadir, which is solved from the second-order system frequency
response model considering the governor dynamics and three types of FFR. The
simulation results in the IEEE 39-bus system with different types of FFR
demonstrate that the proposed method provides accurate and fast prediction for
the frequency nadir under various disturbances
Face alignment using local hough voting
Abstract â We present a novel Hough voting-based method to improve the efficiency and accuracy of fiducial points localization, which can be conveniently integrated with any global prior model for final face alignment. Specifically, two or more stable facial components (e.g., eyes) are first localized and fixed as anchor points, based on which a separate local voting map is constructed for each fiducial point using kernel density estimation. The voting map allows us to effectively constrain the search region of fiducial points by exploiting the local spatial constraints imposed by it. In addition, a multi-output ridge regression method is adopted to align the voting map and the response map of local detectors to the ground truth map, and the learned transformations are then exploited to further increases the robustness of the algorithm against various appearance variations. Encouraging experimental results are given on several publicly available face databases. I
Generalized Category Discovery in Semantic Segmentation
This paper explores a novel setting called Generalized Category Discovery in
Semantic Segmentation (GCDSS), aiming to segment unlabeled images given prior
knowledge from a labeled set of base classes. The unlabeled images contain
pixels of the base class or novel class. In contrast to Novel Category
Discovery in Semantic Segmentation (NCDSS), there is no prerequisite for prior
knowledge mandating the existence of at least one novel class in each unlabeled
image. Besides, we broaden the segmentation scope beyond foreground objects to
include the entire image. Existing NCDSS methods rely on the aforementioned
priors, making them challenging to truly apply in real-world situations. We
propose a straightforward yet effective framework that reinterprets the GCDSS
challenge as a task of mask classification. Additionally, we construct a
baseline method and introduce the Neighborhood Relations-Guided Mask Clustering
Algorithm (NeRG-MaskCA) for mask categorization to address the fragmentation in
semantic representation. A benchmark dataset, Cityscapes-GCD, derived from the
Cityscapes dataset, is established to evaluate the GCDSS framework. Our method
demonstrates the feasibility of the GCDSS problem and the potential for
discovering and segmenting novel object classes in unlabeled images. We employ
the generated pseudo-labels from our approach as ground truth to supervise the
training of other models, thereby enabling them with the ability to segment
novel classes. It paves the way for further research in generalized category
discovery, broadening the horizons of semantic segmentation and its
applications. For details, please visit https://github.com/JethroPeng/GCDS
Comparative genomics study of polyhydroxyalkanoates (PHA) and ectoine relevant genes from Halomonas sp. TD01 revealed extensive horizontal gene transfer events and co-evolutionary relationships
BACKGROUND: Halophilic bacteria have shown their significance in industrial production of polyhydroxyalkanoates (PHA) and are gaining more attention for genetic engineering modification. Yet, little information on the genomics and PHA related genes from halophilic bacteria have been disclosed so far. RESULTS: The draft genome of moderately halophilic bacterium, Halomonas sp. TD01, a strain of great potential for industrial production of short-chain-length polyhydroxyalkanoates (PHA), was analyzed through computational methods to reveal the osmoregulation mechanism and the evolutionary relationship of the enzymes relevant to PHA and ectoine syntheses. Genes involved in the metabolism of PHA and osmolytes were annotated and studied in silico. Although PHA synthase, depolymerase, regulator/repressor and phasin were all involved in PHA metabolic pathways, they demonstrated different horizontal gene transfer (HGT) events between the genomes of different strains. In contrast, co-occurrence of ectoine genes in the same genome was more frequently observed, and ectoine genes were more likely under coincidental horizontal gene transfer than PHA related genes. In addition, the adjacent organization of the homologues of PHA synthase phaC1 and PHA granule binding protein phaP was conserved in the strain TD01, which was also observed in some halophiles and non-halophiles exclusively from Îł-proteobacteria. In contrast to haloarchaea, the proteome of Halomonas sp. TD01 did not show obvious inclination towards acidity relative to non-halophilic Escherichia coli MG1655, which signified that Halomonas sp. TD01 preferred the accumulation of organic osmolytes to ions in order to balance the intracellular osmotic pressure with the environment. CONCLUSIONS: The accessibility of genome information would facilitate research on the genetic engineering of halophilic bacteria including Halomonas sp. TD01
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