93 research outputs found
Blooms of the woloszynskioid dinoflagellate Tovellia diexiensis sp nov (Dinophyceae) in Baishihai Lake at the eastern edge of Tibetan Plateau
Freshwater red tides due to dinoflagellates have caused spectacular and regular "summer reddening" in recent years in Baishihai Lake, a temperate, meromictic, meso- or oligotrophic, high-altitude, landslide-dammed, deep lake located at the eastern edge of Tibetan Plateau in China. Based on morphological and molecular analyses, the causative organism has been identified as a new woloszynskioid dinoflagellate, Tovellia diexiensis Q. Zhang et G.X. Liu sp. nov. The vegetative cells are 20-32 mu m long and 16-24 mu m wide. They have a hemispherical episome and a broadly rounded hyposome with a short characteristic antapical spine. Usually cells are bright red due to the presence of numerous red-pigmented bodies, which often masked the yellowish green discoid chloroplasts. The amphiesma of motile cells comprise mainly quadrilateral, pentagonal or hexagonal thin plates, arranged in 4-5 latitudinal series on the episome, 1 in the cingulum and 4 on, the hyposome. Molecular phylogenies based on small subunit ribosomal DNA and large subunit ribosomal DNA (LSU) indicate T diexiensis from Baishihai Lake to belong to the family Tovelliaceae, which was monophyletic in our LSU phylogenies. During the bloom-forming period in 2005, cell density of T diexiensis reached 9.15 x 10(5) cells L-1. Astaxanthin and its diester were found to be the major pigments in T diexiensis, resulting in a characteristic blood-red color of the water in Baishihai Lake.</p
Point Cloud Quality Assessment using 3D Saliency Maps
Point cloud quality assessment (PCQA) has become an appealing research field
in recent days. Considering the importance of saliency detection in quality
assessment, we propose an effective full-reference PCQA metric which makes the
first attempt to utilize the saliency information to facilitate quality
prediction, called point cloud quality assessment using 3D saliency maps
(PQSM). Specifically, we first propose a projection-based point cloud saliency
map generation method, in which depth information is introduced to better
reflect the geometric characteristics of point clouds. Then, we construct point
cloud local neighborhoods to derive three structural descriptors to indicate
the geometry, color and saliency discrepancies. Finally, a saliency-based
pooling strategy is proposed to generate the final quality score. Extensive
experiments are performed on four independent PCQA databases. The results
demonstrate that the proposed PQSM shows competitive performances compared to
multiple state-of-the-art PCQA metrics
Revisiting Transferable Adversarial Image Examples: Attack Categorization, Evaluation Guidelines, and New Insights
Transferable adversarial examples raise critical security concerns in
real-world, black-box attack scenarios. However, in this work, we identify two
main problems in common evaluation practices: (1) For attack transferability,
lack of systematic, one-to-one attack comparison and fair hyperparameter
settings. (2) For attack stealthiness, simply no comparisons. To address these
problems, we establish new evaluation guidelines by (1) proposing a novel
attack categorization strategy and conducting systematic and fair
intra-category analyses on transferability, and (2) considering diverse
imperceptibility metrics and finer-grained stealthiness characteristics from
the perspective of attack traceback. To this end, we provide the first
large-scale evaluation of transferable adversarial examples on ImageNet,
involving 23 representative attacks against 9 representative defenses. Our
evaluation leads to a number of new insights, including consensus-challenging
ones: (1) Under a fair attack hyperparameter setting, one early attack method,
DI, actually outperforms all the follow-up methods. (2) A state-of-the-art
defense, DiffPure, actually gives a false sense of (white-box) security since
it is indeed largely bypassed by our (black-box) transferable attacks. (3) Even
when all attacks are bounded by the same norm, they lead to dramatically
different stealthiness performance, which negatively correlates with their
transferability performance. Overall, our work demonstrates that existing
problematic evaluations have indeed caused misleading conclusions and missing
points, and as a result, hindered the assessment of the actual progress in this
field.Comment: Code is available at
https://github.com/ZhengyuZhao/TransferAttackEva
Deadzone compensation control based on detection of micro flow rate in pilot stage of proportional directional valve
The pilot operated proportional directional valves (POPDVs) with a flow rate ranging from 100 to 1000 L/min are widely used in electro-hydraulic systems (EHSs). The deadzone of the pilot stage valve and its control compensation could significantly affect the position control performance for the main stage valve that could directly affect dynamics of EHSs In this paper, it is concluded that micro flow rates exist at the intermediate position of the valve based on the analysis of the continuity equation of the flow in the control chamber of the pilot stage. The micro flow rate is helpful to eliminate the discontinuity and unsmooth domain in the previous inverse deadzone compensation function. An improved deadzone detection method is proposed to calibrate the pilot valve flow characteristics which include the micro flow rate. This new method avoids the threshold selection of the main valve spool displacement which affects the detected deadzone values. Its detection processes are realized based on the pilot flow rate characterized by the speed of the main valve spool and the pilot valve displacement characterized by the solenoid current. The deadzone compensation control strategy based on the improved deadzone detection method is also designed. The experimental results using the steady-state position tracking and sinusoidal position tracking methods are verified. It is concluded that the tracking accuracy of the main valve spool position is effectively improved with this control strategy
Prevention of post-surgical abdominal adhesions by a novel biodegradable thermosensitive PECE hydrogel.
<p>Abstract</p> <p>Background</p> <p>Post-operative peritoneal adhesions are common and serious complications for modern medicine. We aim to prevent post-surgical adhesions using biodegradable and thermosensitive poly(ethylene glycol)-poly(ε-caprolactone)-poly(ethylene glycol) (PEG-PCL-PEG, PECE) hydrogel. In this work, we investigated the effect of PECE hydrogel on preventing post-surgical abdominal adhesions in mouse and rat models.</p> <p>Results</p> <p>The PECE hydrogel in sol state could be transformed into gel in less than 20 s at 37°C. In addition, the PECE hydrogel could be easily adhered to the damaged peritoneal surfaces, and be gradually degraded and absorbed by the body within 14 days along with the healing of peritoneal wounds. A notable efficacy of the PECE hydrogel in preventing peritoneal adhesions was demonstrated in the animal models. In contrast, all untreated animals developed adhesions requiring sharp dissection. Furthermore, no significant histopathological changes were observed in main organs of the hydrogel-treated animals.</p> <p>Conclusion</p> <p>Our results suggested that the thermosensitive PECE hydrogel was an effective, safe, and convenient agent on preventing post-surgical intro-abdominal adhesions.</p
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