175 research outputs found
Undulatory Swimming in Viscoelastic Fluids
The effects of fluid elasticity on the swimming behavior of the nematode Caenorhabditis elegans are experimentally investigated by tracking the nematode’s motion and measuring the corresponding velocity fields. We find that fluid elasticity hinders self-propulsion. Compared to Newtonian solutions, fluid elasticity leads to up to 35% slower propulsion. Furthermore, self-propulsion decreases as elastic stresses grow in magnitude in the fluid. This decrease in self-propulsion in viscoelastic fluids is related to the stretching of flexible molecules near hyperbolic points in the flow
WavePF: A Novel Fusion Approach based on Wavelet-guided Pooling for Infrared and Visible Images
Infrared and visible image fusion aims to generate synthetic images
simultaneously containing salient features and rich texture details, which can
be used to boost downstream tasks. However, existing fusion methods are
suffering from the issues of texture loss and edge information deficiency,
which result in suboptimal fusion results. Meanwhile, the straight-forward
up-sampling operator can not well preserve the source information from
multi-scale features. To address these issues, a novel fusion network based on
the wavelet-guided pooling (wave-pooling) manner is proposed, termed as WavePF.
Specifically, a wave-pooling based encoder is designed to extract multi-scale
image and detail features of source images at the same time. In addition, the
spatial attention model is used to aggregate these salient features. After
that, the fused features will be reconstructed by the decoder, in which the
up-sampling operator is replaced by the wave-pooling reversed operation.
Different from the common max-pooling technique, image features after the
wave-pooling layer can retain abundant details information, which can benefit
the fusion process. In this case, rich texture details and multi-scale
information can be maintained during the reconstruction phase. The experimental
results demonstrate that our method exhibits superior fusion performance over
the state-of-the-arts on multiple image fusion benchmark
Research on the optimal capacity configuration of green storage microgrid based on the improved sparrow search algorithm
Green storage plays a key role in modern logistics and is committed to minimizing the environmental impact. To promote the transformation of traditional storage to green storage, research on the capacity allocation of wind-solar-storage microgrids for green storage is proposed. Firstly, this paper proposes a microgrid capacity configuration model, and secondly takes the shortest payback period as the objective function, and uses the improved sparrow search algorithm (ISSA) for optimization. Firstly, the Logistic-Tent compound chaotic mapping method is added to the population initialization of the sparrow search algorithm (SSA). Secondly, the adaptive t-distribution mutation is used to improve the discoverer, and the overall optimization ability of the algorithm is improved. Finally, the hybrid decreasing strategy is adopted in the process of vigilance position update. The ISSA can improve the search efficiency of the algorithm, avoid premature convergence and enhance the robustness of the algorithm, which is helpful to better apply to the optimal configuration of wind-solar-storage microgrid capacity in green storage. By analyzing the optimal capacity allocation results of two typical days, the system can better adapt to the dynamic storage requirements and improve the flexibility and sustainability of the supply chain
Fluid-Induced Propulsion of Rigid Particles in Wormlike Micellar Solutions
In the absence of inertia, a reciprocal swimmer achieves no net motion in a
viscous Newtonian fluid. Here, we investigate the ability of a reciprocally
actuated particle to translate through a complex fluid that possesses a network
using tracking methods and birefringence imaging. A geometrically polar
particle, a rod with a bead on one end, is reciprocally rotated using magnetic
fields. The particle is immersed in a wormlike micellar (WLM) solution that is
known to be susceptible to the formation of shear bands and other localized
structures due to shear-induced remodeling of its microstructure. Results show
that the nonlinearities present in this WLM solution break time-reversal
symmetry under certain conditions, and enable propulsion of an artificial
"swimmer." We find three regimes dependent on the Deborah number (De): net
motion towards the bead-end of the particle at low De, net motion towards the
rod-end of the particle at intermediate De, and no appreciable propulsion at
high De. At low De, where the particle time-scale is longer then the fluid
relaxation time, we believe that propulsion is caused by an imbalance in the
fluid first normal stress differences between the two ends of the particle
(bead and rod). At De~1, however, we observe the emergence of a region of
network anisotropy near the rod using birefringence imaging. This anisotropy
suggests alignment of the micellar network, which is "locked in" due to the
shorter time-scale of the particle relative to the fluid
A High-Gain Observer-Based Adaptive Super-Twisting Algorithm for DC-Link Voltage Control of NPC Converters
Acting as an interface between the grid and many energy systems, the active front-end (AFE)
has been widely used in a large variety of industrial applications. In this paper, in order to ensure the
fast dynamic performance and good disturbance rejection ability of the AFE, a high-gain observer
(HGO) plus adaptive super-twisting algorithm (STA) for the three-level neutral-point-clamped (NPC)
converter is proposed. Comparing with the conventional PI control strategy, the proposed controller
implements the adaptive STA in the voltage regulator to provide a faster transient response. The gains
of the adaptive STA keep varying according to the rules being reduced in steady state but increasing in
transient conditions. Therefore, the chattering phenomenon is mitigated and the dynamic response is
guaranteed. Additionally, to undermine the impact of external disturbances on the dc-link voltage, a
high-efficiency HGO is designed in the voltage regulation loop to reject it. Experimental results based
on a three-level NPC prototype are given and compared with the conventional PI method to validate
the fast dynamic performance and high disturbance rejection ability of the proposed approach.National Key R&D Program of China SQ2019YFB130028National Natural Science Foundation of China 61525303National Natural Science Foundation of China 41772377National Natural Science Foundation of China 61673130Self-Planned Task of State Key Laboratory of Robotics and System (HIT) SKLRS201806BMinisterio de Economía y Competitividad TEC2016-78430-RJunta de Andalucía P18-RT-1340Fondo de Investigación Nacional de Qatar NPRP 9-310-2-13
Supplementation of hyaluronic acid injections with vitamin D improve knee function by attenuating synovial fluid oxidative stress in osteoarthritis patients with vitamin D insufficiency
ObjectivesThere is still controversy about the effect of vitamin D supplementation on osteoarthritis (OA). The purpose of this study was to investigate the effects of vitamin D supplementation with Hyaluronic acid (HA) injection on OA.MethodsWe investigated serum vitamin D levels and oxidative stress (OS) in synovial fluid from patients with OA who underwent total knee arthroplasty (grade IV, n = 24) and HA injection (grade II and III, n = 40). The effects of HA injection with or without oral vitamin D supplementation on synovial fluid OS and knee pain and function were then further investigated. Finally, patients underwent HA injection were divided into two groups according to vitamin D levels (vitamin D < or > 30 ng/ml), and the efficacy of the two groups were compared.ResultsThe results showed that the levels of glutathione peroxidase (GSH-PX) (P < 0.05) in the synovial fluid were lower in patients with stage IV OA than that in patients with stage II-III OA, while the levels of malondialdehyde (MDA) (P < 0.05) and lactate dehydrogenase (LDH) (P < 0.01) were significantly higher. Moreover, we found that age, BMI and vitamin D levels were significantly associated with the levels of oxidants and/or antioxidants in synovial fluid, and that vitamin D was significantly negatively correlated with BMI (R = −0.3527, p = 0.0043). Supplementation of HA injections with vitamin D significantly reduced the OS status in synovial fluid, attenuated knee pain and improved knee function in OA patients with vitamin D insufficiency.ConclusionWe conclude that maintenance of vitamin D sufficiency may be beneficial for the treatment of OA by improving OS in synovial fluid
Polymorphisms on SSC15q21-q26 Containing QTL for reproduction in Swine and its association with litter size
Several quantitative trait loci (QTL) for important reproductive traits (ovulation rate) have been identified on the porcine chromosome 15 (SSC15). To assist in the selection of positional candidate swine genes for these QTL on SSC15, twenty-one genes had already been assigned to SSC15 in a previous study in our lab, by using the radiation hybrid panel IMpRH. Further polymorphism studies were carried out on these positional candidate genes with four breeds of pigs (Duroc, Erhualian, Dahuabai and Landrace) harboring significant differences in reproduction traits. A total of nineteen polymorphisms were found in 21 genes. Among these, seven in six genes were used for association studies, whereby NRP2 polymorphism was found to be significantly (p < 0.05) associated with litter-size traits. NRP2 might be a candidate gene for pig-litter size based on its chromosome location (Du et al., 2006), significant association with litter-size traits and relationships with Sema and the VEGF super families
Finishing the euchromatic sequence of the human genome
The sequence of the human genome encodes the genetic instructions for human physiology, as well as rich information about human evolution. In 2001, the International Human Genome Sequencing Consortium reported a draft sequence of the euchromatic portion of the human genome. Since then, the international collaboration has worked to convert this draft into a genome sequence with high accuracy and nearly complete coverage. Here, we report the result of this finishing process. The current genome sequence (Build 35) contains 2.85 billion nucleotides interrupted by only 341 gaps. It covers ∼99% of the euchromatic genome and is accurate to an error rate of ∼1 event per 100,000 bases. Many of the remaining euchromatic gaps are associated with segmental duplications and will require focused work with new methods. The near-complete sequence, the first for a vertebrate, greatly improves the precision of biological analyses of the human genome including studies of gene number, birth and death. Notably, the human enome seems to encode only 20,000-25,000 protein-coding genes. The genome sequence reported here should serve as a firm foundation for biomedical research in the decades ahead
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